SYSTEMS AND METHODS FOR PRODUCING WASH OIL

Abstract

Systems and methods for producing a wash oil using a light fuel oil (e.g., cracked distillate) are disclosed. The methods include hydrogenating the cracked distillate and separating the hydrogenated cracked distillate to remove C.sub.4 to C.sub.6 hydrocarbons to produce the wash oil.

Claims

1. A method of processing a light fuel oil, the method comprising: hydrogenating the light fuel oil to produce a hydrogenated light fuel oil; and separating, in a separation unit, the hydrogenated light fuel oil to produce a wash oil stream.

2. A method of processing a cracked distillate, the method comprising: hydrogenating the cracked distillate and diluent comprising pyrolysis gas in a hydrogenation unit to produce a hydrogenated intermediate stream; and separating, in a separation unit, the hydrogenated intermediate stream to remove C.sub.4 to C.sub.6 hydrocarbons, toluene and xylene from the hydrogenated intermediate stream to produce a wash oil stream configured to remove fouling from equipment.

3. The method of claim 2, wherein the equipment includes a compressor, a heat exchanger, or combinations thereof.

4. The method of claim 2, wherein the hydrogenating step is configured to saturate unsaturated hydrocarbons of the cracked distillate.

5. The method of claim 2, wherein the separation unit comprises one or more distillation columns.

6. The method of claim 2, wherein the compressor includes a cracked gas compressor.

7. The method of claim 2, wherein the fouling comprises one or more polymers formed by unsaturated hydrocarbons, indene, (methyl)-styrene, butadiene, dicyclopentadiene (DCPD), (methyl)-indene, or combinations thereof.

8. The method of claim 2, wherein the cracked distillate is produced via steam cracking of hydrocarbons.

9. The method of claim 2, wherein the cracked distillate comprises 90 to 95 wt. % aromatics.

10. The method of claim 2, wherein the wash oil stream comprises 90 to 99 wt. % aromatics.

11. The method of claim 2, wherein the pyrolysis gas is produced via condensation of cracked gas in quench water tower or cracked gas compressor.

12. The method of claim 2, wherein the cracked distillate and the pyrolysis gas stream are flowed into the hydrogenation unit at a weight flow rate ratio of 1:80 to 1:50.

13. The method of claim 2, wherein the hydrogenation unit is operated at an operating temperature of 50 to 175 C.

14. The method of claim 2, wherein the hydrogenation unit is operated at an operating pressure of 30 to 50 bar.

15. The method of claim 2, wherein the wash oil is configured to rinse off fouling from compressor internals and/or interstage coolers of a crack gas compressor.

16. The method of claim 2, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

17. The method of claim 2, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

18. The method of claim 4, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

19. The method of claim 5, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

20. The method of claim 6, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0026] FIG. 1 shows a schematic diagram of a system for producing a wash oil, according to embodiments of the invention; and

[0027] FIG. 2 shows a schematic flowchart of a method for producing a wash oil, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Currently, wash oils used in chemical plants generally have low gum content and high aromatic content to ensure good quality. Thus, the conventional wash oils usually are expensive to produce. Using these conventional wash oils for removing fouling can considerably increase the overall cost for various chemical and/or oil production processes. Thus, conventional wash oils are used for intermittent washing. The present invention provides a solution to this problem. The solution is premised on a method of processing a light fuel oil including a cracked distillate. The method comprises hydrogenating the light fuel oil (e.g., cracked distillate) and separating the hydrogenated light fuel oil (e.g., cracked distillate) to produce the wash oil. This can be beneficial as the disclosed methods use conventionally low valued light fuel oils such as cracked distillate as a feedstock, thereby reducing the cost for obtaining the wash oil and increasing the overall value of cracked distillate. Additionally, due to low cost for the light fuel oil, the wash oil produced by the disclosed method can be used for continuous removing of fouling from equipment. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. System for Producing Wash Oil

[0029] In embodiments of the invention, the system for processing a light fuel oil (e.g., a cracked distillate) is capable of reducing the wash oil cost for removing fouling from equipment including a compressor and/or a heat exchanger, soaking fouled equipment, and/or flushing fouled equipment, compared to using a conventional commercial wash oil. With reference to FIG. 1, a schematic diagram is shown for system 100, which is used for processing a light fuel oil (e.g., a cracked distillate) to produce a wash oil.

[0030] According to embodiments of the invention, system 100 includes primary fractionator 101 configured to separate a product stream from a steam cracker to produce first stream 11. First stream 11 may comprise cracked distillate, (indene, methyl) naphthalene, methyl(indene), dimethylethylbenzene, methylstyrene, or combinations thereof. In embodiments of the invention, primary fractionator 101 can include one or more distillation columns.

[0031] According to embodiments of the invention, one of the outlets of primary fractionator is in fluid communication with an inlet of cracked distillate column 102 such that first stream 11 flows from primary fractionator 101 to cracked distillate column 102. Cracked distillate column 102 can be configured to separate first stream 11 to produce cracked distillate stream 12 comprising primarily C.sub.10+ hydrocarbons. Cracked distillated column 102 can include a distillation column. In embodiments of the invention, cracked distillate column 102 is further configured to remove light end of the cracked distillate by using a stripping gas.

[0032] According to embodiments of the invention, an outlet of cracked distillate column 102 is in fluid communication with an inlet of hydrogenation unit 103 such that at least a portion of cracked distillate stream 12, which forms cracked distillate portion 13, flows from cracked distillate column 102 to hydrogenation unit 103. In embodiments of the invention, hydrogenation unit 103 is configured to hydrogenate unsaturated hydrocarbons and/or remove gum forming compounds from cracked distillate portion 13 and/or a diluent stream to produce hydrogenated intermediate stream 15. The diluent stream can be configured to reduce negative impact of heavy components and/or contaminants of cracked distillate portion 13 on catalyst of hydrogenation unit 103. In embodiments of the invention, the diluent stream can include (1) pygas stream 14 including pyrolysis gasoline, and/or (2) another hydrocarbon recycle stream from another chemical plant. In embodiments of the invention, hydrogenation unit 103 can include a multistage hydrogenation unit. Hydrogenated intermediate stream 15 may comprise less than 40 wt. % unsaturated hydrocarbons and/or gum forming compounds. In embodiments of the invention, hydrogenation unit 103 includes a gasoline hydrogenation unit. Hydrogenation unit 103 can include a hydrogenation catalyst comprising nickel, palladium, molybdenum, cobalt, or combinations thereof.

[0033] According to embodiments of the invention, an outlet of gasoline hydrogenation unit 103 is in fluid communication with an inlet of separation unit 110 such that hydrogenated intermediate stream 15 flows from hydrogenation unit 103 to separation unit 110. In embodiments of the invention, separation unit 110 is configured to separate intermediate stream 15 to produce wash oil stream 16 comprising at least 90 wt. % aromatics.

[0034] In embodiments of the invention, separation unit 110 includes C.sub.4 column 104 configured to separate C.sub.4 hydrocarbons from hydrogenated intermediate stream 15 to produce C.sub.5+ stream 17 comprising C.sub.5+ hydrocarbons. An outlet of C.sub.4 column 104 can be in fluid communication with an inlet of C.sub.5 column 105 such that C.sub.5+ stream 17 flows from C.sub.4 column 104 to C.sub.5 column 105. In embodiments of the invention, C.sub.5 column 105 is configured to separate C.sub.5 hydrocarbons from C.sub.5+ hydrocarbons to produce C.sub.6+ stream 18 comprising C.sub.6+ hydrocarbons. An outlet of C.sub.5 column 105 can be in fluid communication with an inlet of C.sub.6 column 106 such that C.sub.6+ stream 18 flows from C.sub.5 column 105 to C.sub.6 column 106. In embodiments of the invention, C.sub.6 column 106 is configured to separate C.sub.6 hydrocarbons from C.sub.6+ stream 18 to form C.sub.7+ stream 19 comprising primarily C.sub.7+ hydrocarbons. According to embodiments of the invention, an outlet of C.sub.6 column 106 is in fluid communication with an inlet of C.sub.5 column 107 such that C.sub.7+ stream 19 flows from C.sub.6 column 106 to C.sub.5 column 107. In embodiments of the invention, C.sub.5 column 107 is configured to separate C.sub.7 to C.sub.8 fraction from C.sub.7+ stream 19 to produce wash oil stream 16 comprising the wash oil, and C.sub.7 to C.sub.8 fraction stream 20 comprising primarily toluene, xylenes (p-, m-, o-), and ethylbenzene, collectively.

B. Method for Processing Cracked Distillate to Produce Wash Oil

[0035] In embodiments of the invention, a method of processing a light fuel oil (e.g., cracked distillate) to produce wash oil is described. As shown in FIG. 2, embodiments of the invention include method 200 for processing cracked distillate for producing wash oil with reduced cost compared to conventional wash oil. Method 200 may be implemented by system 100, as shown in FIG. 1 and described above.

[0036] According to embodiments of the invention, as shown in block 201, method 200 includes flowing a light fuel oil stream (e.g., cracked distillate of cracked distillate portion 13) and/or the diluent (e.g., pyrolysis gas of pygas stream 14) into hydrogenation unit 103. In embodiments of the invention, the cracked distillate and the pyrolysis gas stream are flowed into the hydrogenation unit at a weight flow rate ratio of 1:80 to 1:50 and all ranges and values there between including ranges of 1:80 to 1:70, 1:70 to 1:60, and 1:60 to 1:50. In embodiments of the invention, the cracked distillate is produced via distillate take-off on mid-top of primary fractionator. Pygas stream 14 may be produced via condensation of cracked gas in quench water tower and compressor interstage sections. The cracked distillate comprises primarily C.sub.10+ hydrocarbons. The pyrolysis gas comprises primarily C.sub.4 to C.sub.10 hydrocarbons.

[0037] According to embodiments of the invention, as shown in block 202, method 200 includes hydrogenating the light fuel oil stream (e.g., cracked distillate of cracked distillate portion 13) and the diluent (e.g., pyrolysis gas of pygas stream 14) to produce hydrogenated intermediate stream 15. Hydrogenated intermediate stream 15 may comprises less than 0.5 wt. % reactive molecules. Non-limiting examples of the reactive molecules can include an indene, a styrene, dicyclopentadiene (DCPD), or combinations thereof. Hydrogenated intermediate stream 15 can include 60 to 80 wt. % aromatics. In embodiments of the invention, hydrogenating at block 202 is performed under reaction conditions including a reaction temperature of 50 to 175 C. and all ranges and values there between including ranges of 50 to 55 C., 55 to 65 C., 65 to 75 C., 75 to 85 C., 85 to 95 C., 95 to 105 C., 105 to 115 C., 115 to 125 C., 125 to 135 C., 135 to 145 C., 145 to 155 C., 155 to 165 C., and 165 to 175 C. The reaction conditions at block 202 can further include a reaction pressure of 30 to 50 bar and all ranges and values there between including ranges of 30 to 32 bar, 32 to 34 bar, 34 to 36 bar, 36 to 38 bar, 38 to 40 bar, 40 to 42 bar, 42 to 44 bar, 44 to 46 bar, 46 to 48 bar, and 48 to 50 bar. The reaction conditions at block 202 can include a hydrogen partial pressure of 20 to 30 bar and all ranges and values there between including ranges of 20 to 21 bar, 21 to 22 bar, 22 to 23 bar, 23 to 24 bar, 24 to 25 bar, 25 to 26 bar, 26 to 27 bar, 27 to 28 bar, 28 to 29 bar, and 29 to 30 bar. The reaction conditions at block 202 can include a superficial velocity of 1 to 5 m/s and all ranges and values there between including ranges of 1 to 2 m/s, 2 to 3 m/s, 3 to 4 m/s, and 4 to 5 m/s.

[0038] According to embodiments of the invention, as shown in block 203, method 200 includes separating, in separation unit 110, hydrogenated intermediate stream 15 to remove C.sub.4 (non-condensables) to C.sub.5-8 hydrocarbons, from hydrogenated intermediate stream 15 to produce wash oil stream 16, which is configured to remove fouling from a compressor. In embodiments of the invention, wash oil stream 16 comprises more than 90 wt. % aromatics, preferably 90 to 98 wt. % aromatics and all ranges and values there between including ranges of 90 to 91 wt. %, 91 to 92 wt. %, 92 to 93 wt. %, 93 to 94 wt. %, 94 to 95 wt. %, 95 to 96 wt. %, 96 to 97 wt. %, and 97 to 98 wt. %. Wash oil stream 16, in embodiments of the invention, can have a gum content of 0.2 to 1.5 wt. % and all ranges and values there between including ranges of 0.2 to 0.3 wt. %, 0.3 to 0.4 wt. %, 0.4 to 0.5 wt. %, 0.5 to 0.6 wt. %, 0.6 to 0.7 wt. %, 0.7 to 0.8 wt. %, 0.8 to 0.9 wt. %, 0.9 to 1.0 wt. %, 1.0 to 1.1 wt. %, 1.1 to 1.2 wt. %, 1.2 to 1.3 wt. %, 1.3 to 1.4 wt. %, and 1.4 to 1.5 wt. %.

[0039] In embodiments of the invention, as shown in block 204, separating at block 203 can include separating, in C.sub.4 column 104, hydrogenated intermediate stream 15 to produce C.sub.5+ stream 17 comprising primarily C.sub.5+ hydrocarbons. Separating at block 204 can further produce a C.sub.4 stream comprising primarily C.sub.4 hydrocarbons. In embodiments of the invention, at block 204, C.sub.4 column 104 is operated at an overhead temperature range of 60 to 90 C. and a bottom boiling range of 130 to 150 C. At block 204, C.sub.4 column 104 can be operated at an operating pressure of 4 to 9 barg.

[0040] In embodiments of the invention, as shown in block 205, separating at block 203 can include separating, in C.sub.5 column 105, C.sub.5+ stream 17 to produce C.sub.6+ stream 18 comprising primarily C.sub.6+ hydrocarbons. Separating at block 205 can further produce a C.sub.5 stream comprising primarily C.sub.5 hydrocarbons. In embodiments of the invention, at block 205, C.sub.5 column 105 is operated at an overhead temperature range of 60 to 80 C. and a bottom boiling range of 110 to 140 C. At block 205, C.sub.5 column 105 can be operated at an operating pressure of 1 to 3 barg.

[0041] In embodiments of the invention, as shown in block 206, separating at block 203 can include separating, in C.sub.6 column 106, C.sub.6+ stream 18 to produce C.sub.7+ stream 19 comprising primarily C.sub.7+ hydrocarbons. Separating at block 206 can further produce a C.sub.6 stream comprising primarily C.sub.6 hydrocarbons. In embodiments of the invention, at block 206, C.sub.6 column 106 is operated at an overhead temperature range of 80 to 100 C. and a bottom boiling range of 140 to 165 C. At block 206, C.sub.6 column 106 can be operated at an operating pressure of 1 to 3 barg.

[0042] In embodiments of the invention, as shown in block 207, separating at block 203 can include separating, in C.sub.8 column 107, C.sub.7+ stream 19 to produce wash oil stream 16 comprising the wash oil. Separating at block 207 can further produce a C.sub.7 to C.sub.8 stream comprising primarily C.sub.7 and C.sub.5 fractions, collectively. In embodiments of the invention, at block 207, C.sub.5 column 107 is operated at an overhead temperature range of 70 to 90 C. and a bottom boiling range of 140 to 170 C. At block 207, C.sub.5 column 107 can be operated at an operating pressure of 0.01 to 0.2 bara (vacuum operated column). The wash oil of wash oil stream 16 is configured to remove fouling from a compressor. The compressor can include a cracked gas compressor. The wash oil may be configured to remove fouling from compressor internals and/or interstage coolers of the compressor. The wash oil may be configured to remove fouling from a heat exchanger, soak fouled equipment, and/or flush fouled equipment. The heat exchanger can include a heat exchanger of a quench tower top loop. The fouling can comprise one or more polymers formed by unsaturated hydrocarbons, indene, (methyl)-styrene, butadiene, dicyclopentadiene (DCPD), (methyl)-indene, Diels-Alder polymerization, or combinations thereof.

[0043] Although embodiments of the present invention have been described with reference to blocks of FIG. 2 should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0044] The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

[0045] In the context of the present invention, at least the following 16 embodiments are described. Embodiment 1 is a method of processing a light fuel oil. The method includes hydrogenating the light fuel oil to produce a hydrogenated light fuel oil. The method further includes separating, in a separation unit, the hydrogenated light fuel oil to produce a wash oil stream.

[0046] Embodiment 2 is a method of processing a cracked distillate. The method includes hydrogenating the cracked distillate and diluent containing pyrolysis gas in a hydrogenation unit to produce a hydrogenated intermediate stream. The method further includes separating, in a separation unit, the hydrogenated intermediate stream to remove C.sub.4 to C.sub.6 hydrocarbons, toluene and xylene from the hydrogenated intermediate stream to produce a wash oil stream configured to remove fouling from equipment. Embodiment 3 is the method of any of embodiments 1 and 2, wherein the equipment includes a compressor, a heat exchanger, or combinations thereof. Embodiment 4 is the method of any of embodiments 1 to 3, wherein the hydrogenating step is configured to saturate unsaturated hydrocarbons of the cracked distillate. Embodiment 5 is the method of any of embodiments 1 to 4, wherein the separation unit includes one or more distillation columns. Embodiment 6 is the method of any of embodiments 1 to 5, wherein the compressor includes a cracked gas compressor. Embodiment 7 is the method of any of embodiments 1 to 6, wherein the fouling contains one or more polymers formed by unsaturated hydrocarbons, indene, (methyl)-styrene, butadiene, dicyclopentadiene (DCPD), (methyl)-indene, or combinations thereof. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the cracked distillate is produced via steam cracking of hydrocarbons. Embodiment 9 is the method of any of claims 1 to 8, wherein the cracked distillate contains 90 to 95 wt. % aromatics. Embodiment 10 is the method of any of embodiments 1 to 9, wherein the wash oil stream contains 90 to 99 wt. % aromatics. Embodiment 11 is the method of any of embodiments 1 to 10, wherein the pyrolysis gas is produced via condensation of cracked gas in quench water tower or cracked gas compressor. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the cracked distillate and the pyrolysis gas stream are flowed into the hydrogenation unit at a weight flow rate ratio of 1:80 to 1:50. Embodiment 13 is the method of any of embodiments 1 to 12, wherein the hydrogenation unit is operated at an operating temperature of 50 to 175 C. Embodiment 14 is the method of any of embodiments 1 to 13, wherein the hydrogenation unit is operated at an operating pressure of 30 to 50 bar. Embodiment 15 is the method of any of embodiments 1 to 14, wherein the wash oil is configured to rinse off fouling from compressor internals and/or interstage coolers of a crack gas compressor. Embodiment 16 is the method of any of embodiments 1 to 15, wherein the diluent is configured to reduce negative impact of the cracked distillate on a catalyst used in the hydrogenating step.

[0047] All embodiments described above and herein can be combined in any manner unless expressly excluded.

[0048] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.