System and method for preparing a wash oil

Abstract

Systems and methods for producing wash oil using light fuel oil (e.g., cracked distillate) are disclosed. The method includes hydrogenating the cracked distillate and separating the hydrogenated cracked distillate to remove C4 to C6 hydrocarbons to produce the wash oil.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 130,952, filed December 28, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention generally relates to systems and methods for preparing wash oil. More specifically, this invention relates to systems and methods for preparing wash oil for compressor and soaking purposes using light fuel oil as a raw material. Background Technology

[0004] Wash oils are commonly used to remove scale from equipment in chemical or oil production facilities. Typically, wash oils have relatively strict quality specifications. More specifically, they need to be very "clean," requiring low gum content and high aromatic hydrocarbon content. Therefore, commercially available wash oils are often expensive, increasing the cost of continuous scale removal from equipment.

[0005] Overall, although methods for preparing wash oils exist, improvements are still needed in this field due to the shortcomings of the aforementioned conventional systems and methods. Summary of the Invention

[0006] Solutions have been found to the aforementioned problems related to systems and methods for providing wash oil. These solutions exist in the use of hydrotreated light fuel oils (e.g., hydrotreated cracked fractions, hydrotreated C9+ hydrocarbon streams, and / or hydrotreated C...). 10 (+hydrocarbon stream) is used as a feedstock for wash oil that can be used for continuous removal of scale from equipment. This is at least beneficial in reducing the cost of obtaining wash oil, since hydrotreated cracked fractions are low-cost feedstocks for preparing wash oil. Furthermore, this method can increase the value of light fuel oils such as cracked fractions, which are typically low-value byproducts from steam cracking units, including side streams from primary fractionation columns. Therefore, wash oil prepared by the method of this disclosure can be used for continuous removal of scale from equipment. Thus, the system and method of this disclosure provide a technical solution to problems related to conventional systems and methods for providing wash oil.

[0007] Embodiments of the present invention include a method for processing light fuel oil. The method includes hydrogenating the light fuel oil to produce hydrogenated light fuel oil. The method includes separating the hydrogenated light fuel oil (hydrogenated pure light fuel oil or hydrogenated diluted light fuel oil) in a separation unit to prepare a wash stream.

[0008] Embodiments of the present invention include a method for treating a cracked distillate. The method includes hydrogenating the cracked distillate and a diluent comprising thermally cracked gas in a hydrogenation unit to produce a hydrogenated intermediate stream. The method further includes separating the hydrogenated intermediate stream in a separation unit to remove C4 to C8 hydrocarbons from the hydrogenated intermediate stream, thereby preparing a wash oil stream configured for descaling, primarily for use in cracked gas compressor maintenance.

[0009] Embodiments of the present invention include a method for processing a cracked fraction. The method includes hydrogenating the cracked fraction and thermally cracked gas in a gasoline hydrotreating unit to saturate the unsaturated hydrocarbons of the cracked fraction and produce a hydrogenated intermediate stream. The method further includes separating the hydrogenated intermediate stream in a separation unit comprising one or more distillation columns to remove C4 to C8 hydrocarbons from the hydrogenated intermediate stream, thereby preparing a wash oil stream configured to remove fouling from the cracked gas compressor.

[0010] The following includes definitions of various terms and phrases used in this specification.

[0011] The terms “about” or “approximately” are defined as close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, these terms are defined as deviations within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0012] The terms “weight%”, “volume%”, or “molar%” refer to the weight, volume, or molar percentage of a component based on the total weight, total volume, or total number of moles of the material containing the component, respectively. In a non-limiting example, 10 moles of a component in 100 moles of material is 10 molar% of the component.

[0013] The term “substantially” and its variations are defined to include deviations of less than 10%, less than 5%, less than 1%, or less than 0.5%.

[0014] When used in the claims and / or description, the terms “suppress” or “reduce” or “prevent” or “avoid” or any variations thereof, including any measurable reduction or complete suppression in order to achieve the desired result.

[0015] As used in this specification and / or claims, the term "effective" means suitable for achieving a desired, expected, or anticipated result.

[0016] As used in this specification and / or claims, the term "light fuel oil" refers to fuel primarily containing C 10 + Hydrocarbon stream.

[0017] As used in this specification and / or claims, the term "cracked fraction" refers to the stream obtained from the middle to the top of the primary fractionation column of a liquid vapor cracker.

[0018] As used in this specification and / or claims, the term "wash oil" refers to hydrocarbons containing more than 90% by weight of aromatics and having a boiling point above 300°C.

[0019] As a term used in this specification and / or claims, the term "C" is used in the context of the specification and / or claims. n "+hydrocarbon" where n is a positive integer, such as 1, 2, 3, 4 or 5, refers to any hydrocarbon with at least n carbon atoms per molecule.

[0020] As a term used in this specification and / or claims, the term "C" is used in the context of the specification and / or claims. n "-hydrocarbon" where n is a positive integer, such as 1, 2, 3, 4 or 5, refers to any hydrocarbon with at most n carbon atoms per molecule.

[0021] When used in conjunction with the terms “comprising,” “including,” “containing,” or “having” in the claims or specification, the quantifier preceding an element may indicate “one,” but also has the same meaning as “one or more,” “at least one,” and “one or more than one.”

[0022] The words “contain,” “include,” “have,” or “contain” are inclusive or open-ended and do not exclude other unmentioned elements or methods or steps.

[0023] The method of the present invention may "comprise", "consistently constitute" or "consistent with" specific ingredients, components, compositions, etc. disclosed throughout the specification.

[0024] The term “major” as used in the specification and / or claims means any one of 50% by weight, 50% by mol%, and 50% by volume. For example, “major” can include all values ​​and ranges from 50.1% by weight to 100% by weight, from 50.1% by mol% to 100% by mol%, or from 50.1% by volume to 100% by volume.

[0025] Other objects, features, and advantages of the present invention will become apparent from the following drawings, detailed descriptions, and embodiments. However, it should be understood that while the drawings, detailed descriptions, and embodiments illustrate specific embodiments of the invention, they are given by way of illustration only and are not intended to be limiting. Furthermore, changes and modifications contemplated within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed descriptions. In other embodiments, features from a particular embodiment may be combined with features from other embodiments. For example, a feature from one embodiment may be combined with features from any other embodiment. In other embodiments, additional features may be added to the specific embodiments described herein.

[0026] Brief description of the attached figures

[0027] For a more complete understanding, please refer to the following description in conjunction with the accompanying drawings, in which:

[0028] Figure 1 A schematic diagram of a system for preparing wash oil according to an embodiment of the present invention is shown; and

[0029] Figure 2 A schematic flowchart of a method for preparing wash oil according to an embodiment of the present invention is shown. Detailed Implementation

[0030] Currently, wash oils used in chemical plants generally have low gum content and high aromatic hydrocarbon content to ensure good quality. Therefore, the preparation cost of conventional wash oils is usually very high. Using these conventional wash oils to remove scale significantly increases the total cost of various chemical and / or oil preparation processes. Therefore, conventional wash oils are used for intermittent washing. This invention provides a solution to the above-mentioned problems. The premise of this solution is a method for processing light fuel oils comprising cracked fractions. This method includes hydrogenating the light fuel oil (e.g., cracked fractions) and separating the hydrogenated light fuel oil (e.g., cracked fractions) to prepare wash oil. This can be advantageous because the disclosed method uses conventional low-value light fuel oils such as cracked fractions as feedstock, thereby reducing the cost of obtaining wash oil and increasing the overall value of the cracked fractions. Furthermore, due to the low cost of light fuel oils, the wash oil prepared by the disclosed method can be used for continuous scale removal from equipment. These and other non-limiting aspects of the invention will be discussed in further detail in the following sections.

[0031] A. A system for preparing wash oil

[0032] In embodiments of the invention, systems for treating light fuel oils (e.g., cracked fractions) can reduce the cost of wash oils used to remove scale from, soak, and / or flush scaled equipment from equipment including compressors and / or heat exchangers, compared to the use of conventional commercially available wash oils. (See also...) Figure 1 The diagram shows a schematic of system 100 for processing light fuel oil (e.g., cracked fractions) to prepare wash oil.

[0033] According to an embodiment of the invention, system 100 includes a primary fractionation column 101 configured to separate a product stream from a steam cracker to produce a first stream 11. The first stream 11 may contain cracked fractions, (indene, methyl)naphthalene, methyl(indene), 1,3-dimethyl-4-ethylbenzene, methylstyrene, or combinations thereof. In embodiments of the invention, the primary fractionation column 101 may include one or more distillation columns.

[0034] According to an embodiment of the invention, one of the outlets of the primary fractionation column is in fluid communication with the inlet of the cracking fractionation column 102, such that a first stream 11 flows from the primary fractionation column 101 to the cracking fractionation column 102. The cracking fractionation column 102 can be configured to separate the first stream 11 to produce a product primarily containing C. 10 +Cracked hydrocarbon fraction 12. Cracked fraction column 102 may include a distillation column. In embodiments of the invention, cracked fraction column 102 is also configured to remove the light fraction of the cracked fraction by using stripping gas.

[0035] According to an embodiment of the invention, the outlet of the cracking fractionation tower 102 is in fluid communication with the inlet of the hydrogenation unit 103, such that at least a portion of the cracked fraction stream 12 forming the cracked fraction portion 13 flows from the cracking fractionation tower 102 to the hydrogenation unit 103. In an embodiment of the invention, the hydrogenation unit 103 is configured to hydrogenate unsaturated hydrocarbons and / or remove gum-forming compounds from the cracked fraction portion 13 and / or the diluent stream to produce a hydrogenated intermediate stream 15. The diluent stream can be configured to reduce the negative impact of heavy components and / or contaminants of the cracked fraction portion 13 on the catalyst of the hydrogenation unit 103. In an embodiment of the invention, the diluent stream may comprise (1) a thermally cracked gas stream 14 containing thermally cracked gasoline, and / or (2) another hydrocarbon recycle stream from another chemical plant. In an embodiment of the invention, the hydrogenation unit 103 may comprise a multi-stage hydrogenation unit. The hydrogenated intermediate stream 15 may comprise less than 40% by weight of unsaturated hydrocarbons and / or gum-forming compounds. In an embodiment of the invention, the hydrogenation device 103 includes a gasoline hydrogenation device. The hydrogenation device 103 may contain a hydrogenation catalyst of nickel, palladium, molybdenum, cobalt, or a combination thereof.

[0036] According to an embodiment of the invention, the outlet of the gasoline hydrotreating unit 103 is in fluid communication with the inlet of the separation unit 110, such that the hydrotreated intermediate stream 15 flows from the hydrotreating unit 103 to the separation unit 110. In an embodiment of the invention, the separation unit 110 is configured to separate the intermediate stream 15 to prepare a wash oil stream 16 containing at least 90% by weight aromatics.

[0037] In an embodiment of the invention, the separation device 110 includes a C4 column 104 configured to separate C4 hydrocarbons from a hydrogenated intermediate stream 15 to produce a C5+ stream 17 containing C5+ hydrocarbons. The outlet of the C4 column 104 is in fluid communication with the inlet of a C5 column 105, such that the C5+ stream 17 flows from the C4 column 104 to the C5 column 105. In an embodiment of the invention, the C5 column 105 is configured to separate C5 hydrocarbons from the C5+ hydrocarbons to produce a C6+ stream 18 containing C6+ hydrocarbons. The outlet of the C5 column 105 is in fluid communication with the inlet of a C6 column 106, such that the C6+ stream 18 flows from the C5 column 105 to the C6 column 106. In an embodiment of the invention, the C6 column 106 is configured to separate C6 hydrocarbons from the C6+ stream 18 to form a C7+ stream 19 primarily containing C7+ hydrocarbons. According to an embodiment of the invention, the outlet of C6 column 106 is in fluid communication with the inlet of C8 column 107, such that C7+ stream 19 flows from C6 column 106 to C8 column 107. In an embodiment of the invention, C8 column 107 is configured to separate C7 to C8 fractions from C7+ stream 19 to generate a wash oil stream 16 containing wash oil, and a C7 to C8 fraction stream 20 mainly containing toluene, xylene (p-, m-, o-) and ethylbenzene.

[0038] B. Methods for processing cracked fractions to prepare wash oil

[0039] In embodiments of the invention, a method for processing light fuel oil (e.g., cracked fractions) to prepare wash oil is described. Figure 2 As shown, embodiments of the present invention include a method 200 for processing a cracked fraction of wash oil used to prepare wash oil with reduced costs compared to conventional wash oil. Method 200 can be implemented by system 100, such as... Figure 1 As shown and as described above.

[0040] According to an embodiment of the invention, as shown in block 201, method 200 includes flowing a light fuel oil stream (e.g., a cracked fraction of cracked fraction portion 13) and / or a diluent (e.g., thermally cracked gas from thermally cracked gas stream 14) into a hydrogenation unit 103. In an embodiment of the invention, the cracked fraction and the thermally cracked gas stream flow into the hydrogenation unit at a weight flow rate ratio of 1:80 to 1:50, and including all ranges and values ​​between 1:80 to 1:70, 1:70 to 1:60, and 1:60 to 1:50. In an embodiment of the invention, the cracked fraction is generated by the fraction effluent from the middle top of a primary fractionation column. Thermally cracked gas stream 14 can be generated by condensing the cracked gas in a quench tower and between compressor stages. The cracked fraction primarily contains C 10 +hydrocarbons. Thermally cracked gases mainly contain C4 to C6 hydrocarbons. 10 hydrocarbon.

[0041] According to an embodiment of the invention, as shown in block 202, method 200 includes hydrogenating a light fuel oil stream (e.g., a cracked fraction of cracked fractionation 13) and a diluent (e.g., a thermally cracked gas stream 14) to produce a hydrogenated intermediate stream 15. The hydrogenated intermediate stream 15 may contain less than 0.5% by weight of an active molecule. Non-limiting examples of active molecules may include indene, styrene, dicyclopentadiene (DCPD), or combinations thereof. The hydrogenated intermediate stream 15 may include 60% to 80% by weight of aromatics. In an embodiment of the invention, in block 202, hydrogenation is carried out under reaction conditions including reaction temperatures of 50°C to 175°C and all ranges and values ​​therebetween: 50°C to 55°C, 55°C to 65°C, 65°C to 75°C, 75°C to 85°C, 85°C to 95°C, 95°C to 105°C, 105°C to 115°C, 115°C to 125°C, 125°C to 135°C, 135°C to 145°C, 145°C to 155°C, 155°C to 165°C, and 165°C to 175°C. In block 202, the reaction conditions may further include pressures ranging from 30 bar to 50 bar, and including all ranges and values ​​between 30 bar and 32 bar, 32 bar and 34 bar, 34 bar and 36 bar, 36 bar and 38 bar, 38 bar and 40 bar, 40 bar and 42 bar, 42 bar and 44 bar, 44 bar and 46 bar, 46 bar and 48 bar and 50 bar. In block 202, the reaction conditions may include hydrogen partial pressures ranging from 20 bar to 30 bar, and including all ranges and values ​​between 20 bar and 21 bar, 21 bar and 22 bar, 22 bar and 23 bar, 23 bar and 24 bar, 24 bar and 25 bar, 25 bar and 26 bar, 26 bar and 27 bar, 27 bar and 28 bar, 28 bar and 29 bar and 30 bar. In block 202, the reaction conditions may include empty tower velocities ranging from 1 m / s to 5 m / s and including all ranges and values ​​between 1 m / s to 2 m / s, 2 m / s to 3 m / s, 3 m / s to 4 m / s and 4 m / s to 5 m / s.

[0042] According to an embodiment of the invention, as shown in block 203, method 200 includes separating the hydrogenated intermediate stream 15 from the hydrogenated intermediate stream 15 in a separation device 110 to remove C. 4- (Non-condensable) to C 5-8Hydrocarbons are used to prepare a wash oil stream 16 configured to remove scale from a compressor. In embodiments of the invention, the wash oil stream 16 contains more than 90 wt% aromatics, preferably 90 wt% to 98 wt% aromatics, and aromatics in all ranges and values ​​between 90 wt% to 91 wt%, 91 wt% to 92 wt%, 92 wt% to 93 wt%, 93 wt% to 94 wt%, 94 wt% to 95 wt%, 95 wt% to 96 wt%, 96 wt% to 97 wt%, and 97 wt% to 98 wt%. In embodiments of the invention, the gum content of the wash oil stream 16 can be from 0.2 wt% to 1.5 wt%, and can be any range and value between 0.2 wt% to 0.3 wt%, 0.3 wt% to 0.4 wt%, 0.4 wt% to 0.5 wt%, 0.5 wt% to 0.6 wt%, 0.6 wt% to 0.7 wt%, 0.7 wt% to 0.8 wt%, 0.8 wt% to 0.9 wt%, 0.9 wt% to 1.0 wt%, 1.0 wt% to 1.1 wt%, 1.1 wt% to 1.2 wt%, 1.2 wt% to 1.3 wt%, 1.3 wt% to 1.4 wt%, and 1.4 wt% to 1.5 wt%.

[0043] In an embodiment of the invention, as shown in block 204, the separation in block 203 may include separating the hydrogenated intermediate stream 15 in a C4 column 104 to produce a C5+ stream 17 primarily containing C5+ hydrocarbons. The separation in block 204 may also include producing a C4- stream primarily containing C4- hydrocarbons. In an embodiment of the invention, in block 204, the C4 column 104 is operated at a top temperature of 60°C to 90°C and a bottom boiling point of 130°C to 150°C. In block 204, the C4 column 104 may be operated at an operating pressure of 4 bar to 9 bar.

[0044] In an embodiment of the invention, as shown in block 205, the separation in block 203 may include separating a C5+ stream 17 in a C5 column 105 to produce a C6+ stream 18 primarily containing C6+ hydrocarbons. The separation in block 205 may also include producing a C5 stream primarily containing C5 hydrocarbons. In an embodiment of the invention, in block 205, the C5 column 105 operates at a top temperature of 60°C to 80°C and a bottom boiling point of 110°C to 140°C. In block 205, the C5 column 105 may operate at an operating pressure of 1 bar to 3 bar.

[0045] In an embodiment of the invention, as shown in block 206, the separation in block 203 may include separating a C6+ stream 18 in a C6 column 106 to produce a C7+ stream 19 primarily containing C7+ hydrocarbons. The separation in block 206 may also include producing a C6 stream primarily containing C6 hydrocarbons. In an embodiment of the invention, in block 206, the C6 column 106 operates at a top temperature of 80°C to 100°C and a bottom boiling point of 140°C to 165°C. In block 206, the C6 column 106 may operate at an operating pressure of 1 bar to 3 bar.

[0046] In an embodiment of the invention, as shown in block 207, separation in block 203 may include separating C7+ stream 19 in C8 column 107 to produce wash oil stream 16 primarily containing wash oil. Separation in block 207 may also include producing C7 and C8 streams primarily containing C7 to C8 fractions. In an embodiment of the invention, in block 207, C8 column 107 operates at a top temperature of 70°C to 90°C and a bottom boiling point of 140°C to 170°C. In block 207, C8 column 107 may operate at an operating pressure of 0.01 bar to 0.2 bar (vacuum-operated column). The wash oil in wash oil stream 16 is configured to remove scale from a compressor. The compressor may include a cracked gas compressor. The wash oil may be configured to remove scale from compressor internal components and / or interstage coolers. The wash oil may be configured to remove scale from heat exchangers, equipment for soaking scale, and / or equipment for flushing scale. The heat exchanger may include a heat exchanger in the top loop of a quench tower. Scaling can include one or more polymers formed from unsaturated hydrocarbons, indene, (methyl)-styrene, butadiene, dimercyclopentadiene (DCPD), (methyl)-indene, Diels-Alder polymerization, or combinations thereof.

[0047] Although reference Figure 2 The boxes in the diagram describe embodiments of the present invention. It should be understood that the operation of the present invention is not limited to... Figure 2 The specific boxes and / or the specific box order shown. Therefore, embodiments of the present invention can use different... Figure 2 Different boxes arranged in a specific order provide the functionality described in this article.

[0048] The systems and processes described herein may also include various devices not shown and known to those skilled in the art of chemical processing. For example, some controllers, pipes, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, etc., may not be shown.

[0049] Within the context of this invention, at least 16 embodiments are described. Embodiment 1 is a method for processing light fuel oil. The method includes hydrogenating the light fuel oil to produce hydrogenated light fuel oil. The method further includes separating the hydrogenated light fuel oil in a separation unit to prepare a wash oil stream.

[0050] Embodiment 2 is a method for processing a cracked distillate. The method includes hydrogenating the cracked distillate and a diluent comprising thermally cracked gas in a hydrogenation unit to produce a hydrogenated intermediate stream. The method further includes separating the hydrogenated intermediate stream in a separation unit to remove C4 to C6 hydrocarbons, toluene, and xylene from the hydrogenated intermediate stream, thereby preparing a wash oil stream configured to remove equipment fouling. Embodiment 3 is a method of any one of Embodiments 1 to 2, wherein the equipment includes a compressor, a heat exchanger, or a combination thereof. Embodiment 4 is a method of any one of Embodiments 1 to 3, wherein the hydrogenation step is configured to saturate the unsaturated hydrocarbons of the cracked distillate. Embodiment 5 is a method of any one of Embodiments 1 to 4, wherein the separation unit includes one or more distillation columns. Embodiment 6 is a method of any one of Embodiments 1 to 5, wherein the compressor includes a cracked gas compressor. Embodiment 7 is the method of any one of Embodiments 1 to 6, wherein the scaling comprises one or more polymers formed from unsaturated hydrocarbons, indene, (methyl)-styrene, butadiene, dimercyclopentadiene (DCPD), (methyl)-indene, or combinations thereof. Embodiment 8 is the method of any one of Embodiments 1 to 7, wherein the cracked fraction is produced by steam cracking of hydrocarbons. Embodiment 9 is the method of any one of Embodiments 1 to 8, wherein the cracked fraction contains 90% to 95% by weight aromatics. Embodiment 10 is the method of any one of Embodiments 1 to 9, wherein the wash stream contains 90% to 99% by weight aromatics. Embodiment 11 is the method of any one of Embodiments 1 to 10, wherein the thermal cracking gas is produced by condensing the cracked gas in a quench tower or a cracked gas compressor. Embodiment 12 is the method of any one of Embodiments 1 to 11, wherein the cracked fraction and the thermal cracking gas flow into the hydrogenation unit at a weight flow ratio of 1:80 to 1:50. Embodiment 13 is the method of any one of Embodiments 1 to 12, wherein the hydrotreating unit operates at an operating temperature of 50°C to 175°C. Embodiment 14 is the method of any one of Embodiments 1 to 13, wherein the hydrotreating unit operates at an operating pressure of 30 bar to 50 bar. Embodiment 15 is the method of any one of Embodiments 1 to 14, wherein wash oil is configured to flush scale buildup on the internal components of the cracked gas compressor and / or the interstage cooler. Embodiment 16 is the method of any one of Embodiments 1 to 15, wherein a diluent is configured to reduce the negative impact of the cracked fraction on the catalyst used in the hydrotreating step.

[0051] All the above and the implementation schemes described herein can be combined in any way, unless explicitly excluded.

[0052] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, material compositions, means, methods, and steps described in the specification. As will be readily understood by those skilled in the art from the foregoing disclosure, existing or future-developed processes, machines, manufactures, material compositions, means, methods, or steps that perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein can be utilized. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, means, methods, or steps within their scope.

Claims

1. A method for processing light fuel oil, the method comprising: Hydrogenating light fuel oil to produce a hydrogenated intermediate stream; and The hydrogenated intermediate stream is separated in a separation unit to prepare a C7+ stream; and In a C8 distillation column, the C7+ stream is separated to produce a C7 to C8 fraction stream containing toluene, xylene, and ethylbenzene, and a wash oil stream containing 90% to 99% aromatics with a boiling point above 300°C.

2. The method according to claim 1, wherein the xylene comprises p-xylene, m-xylene, and o-xylene.

3. A method for processing a cracked distillate, the method comprising: In a hydrogenation unit, a cracked fraction and a diluent including thermally cracked gas are hydrogenated at a weight flow rate ratio of 1:80 to 1:50 to reduce the negative impact of the cracked fraction on the catalyst used in the hydrogenation step, in order to produce a hydrogenated intermediate stream. and In a separation unit, a hydrogenated intermediate stream is separated to remove C4 to C6 hydrocarbons, toluene, and xylene from the hydrogenated intermediate stream, thereby preparing a wash oil stream configured to remove equipment scale.

4. The method of claim 3, wherein the equipment comprises a compressor, a heat exchanger, or a combination thereof.

5. The method according to any one of claims 3 to 4, wherein the hydrogenation step is configured to saturate the unsaturated hydrocarbons of the cracked fraction.

6. The method according to any one of claims 3 to 4, wherein the separation device comprises one or more distillation columns, wherein the C8 distillation column is configured to separate C7 to C8 fractions from the C7+ stream to generate a wash oil stream with a boiling point above 300°C.

7. The method according to any one of claims 3 to 4, wherein the compressor comprises a cracked gas compressor.

8. The method according to any one of claims 3 to 4, wherein the scaling comprises one or more polymers formed from unsaturated hydrocarbons.

9. The method according to claim 8, wherein the unsaturated hydrocarbon comprises indene, (methyl)-styrene, butadiene, dicyclopentadiene (DCPD), (methyl)-indene, or combinations thereof.

10. The method according to any one of claims 3 to 4, wherein the cracked fraction is produced by steam cracking of hydrocarbons.

11. The method according to any one of claims 3 to 4, wherein the cracked fraction contains 90% to 95% by weight of aromatics.

12. The method according to any one of claims 3 to 4, wherein the wash oil stream comprises 90% to 99% by weight of aromatics.

13. The method according to any one of claims 3 to 4, wherein the pyrolysis gas is generated by condensing the pyrolysis gas in a quench tower or a pyrolysis gas compressor.

14. The method according to any one of claims 3 to 4, wherein the hydrogenation apparatus is operated at an operating temperature of 50°C to 175°C.

15. The method according to any one of claims 3 to 4, wherein the hydrogenation unit operates at an operating pressure of 30 bar to 50 bar.

16. The method according to any one of claims 3 to 4, wherein the wash oil flow is configured to flush scale buildup on the compressor internals and interstage coolers of the cracked gas compressor.

Images