Process to recover gasoline and diesel from aromatic complex bottoms

Abstract

Systems and methods for crude oil separation and upgrading, which include the ability to reduce aromatic complex bottoms content in gasoline and higher-quality aromatic compounds. In some embodiments, aromatic complex bottoms are recycled for further processing. In some embodiments, aromatic complex bottoms are separated for further processing.

Claims

1. A system for oil separation and upgrading, the system comprising: an inlet stream comprising crude oil; an atmospheric distillation unit (ADU), the ADU in fluid communication with the inlet stream, and operable to separate the inlet stream into an ADU tops stream and an ADU middle stream, the ADU tops stream comprising naphtha, and the ADU middle stream comprising distillate; a naphtha hydrotreating unit (NHT), the NHT in fluid communication with the ADU and operable to treat with hydrogen the naphtha in the ADU tops stream; a naphtha reforming unit (NREF), the NREF in fluid communication with the NHT and operable to reform a hydrotreated naphtha stream produced by the NHT, and the NREF further operable to produce separate hydrogen and reformate streams; an aromatics complex (ARC), the ARC in fluid communication with the NREF and operable to receive the reformate stream produced by the NREF, and the ARC further operable to separate the reformate stream into a gasoline pool stream, an aromatics stream, and an ARC aromatic bottoms stream; a secondary ADU in fluid communication with the ARC aromatic bottoms stream and the ADU middle stream, wherein the secondary ADU is operable to separate the aromatic bottoms stream into a gasoline stream and a stream comprising heavy aromatics; and a kerosene hydrofinishing unit (KHT), the KHT in fluid communication with a distillate inlet stream, the distillate inlet stream comprising fluid flow from the ADU middle stream and the stream comprising heavy aromatics, and the KHT operable to treat the distillate inlet stream with hydrogen.

2. The system according to claim 1, wherein the gasoline stream is used as a gasoline blending component without any further treatment.

3. The system according to claim 1, wherein the KHT comprises a first stage sour hydrotreating section, a second stage sweet aromatic saturation and hydrocracking section with intermediate separation, and a fractionation system.

4. The system according to claim 1, wherein kerosene is produced and is suitable for dual purpose kerosene use according to heating and jet fuel requirements.

5. The system according to claim 1, wherein the aromatic bottoms stream comprises aromatic compounds with boiling points in the range of about 100° C. to about 350° C.

6. A method for oil separation and upgrading, the method comprising the steps of: supplying an inlet stream comprising crude oil; separating the inlet stream into a tops stream and a middle stream, the tops stream comprising naphtha, and the middle stream comprising distillate; treating with hydrogen the naphtha in the tops stream to produce a hydrotreated naphtha stream; reforming the hydrotreated naphtha stream to produce separate hydrogen and reformate streams; separating the reformate stream into a gasoline pool stream, an aromatics stream, and an aromatic bottoms stream; separating the aromatic bottoms stream into a gasoline stream and a stream comprising heavy aromatics; combining the middle stream comprising distillate and the stream comprising heavy aromatics; and treating the middle stream comprising distillate and the stream comprising heavy aromatics with hydrogen.

7. A system for oil separation and upgrading, the system comprising: an inlet stream comprising crude oil; an atmospheric distillation unit (ADU), the ADU in fluid communication with the inlet stream, and operable to separate the inlet stream into an ADU tops stream and an ADU middle stream, the ADU tops stream comprising naphtha, and the ADU middle stream comprising distillate; a naphtha hydrotreating unit (NHT), the NHT in fluid communication with the ADU and operable to treat with hydrogen the naphtha in the ADU tops stream; a naphtha reforming unit (NREF), the NREF in fluid communication with the NHT and operable to reform a hydrotreated naphtha stream produced by the NHT, and the NREF further operable to produce separate hydrogen and reformate streams; an aromatics complex (ARC), the ARC in fluid communication with the NREF and operable to receive the reformate stream produced by the NREF, and the ARC further operable to separate the reformate stream into a gasoline pool stream, an aromatics stream, and an aromatic bottoms stream, wherein the aromatic bottoms stream is in fluid communication with the inlet stream comprising crude oil; and a kerosene hydrofinishing unit (KHT), the KHT in fluid communication with a distillate inlet stream, the distillate inlet stream comprising fluid flow from the ADU middle stream and comprising heavy aromatics from the aromatic bottoms stream, and the KHT operable to treat the distillate inlet stream with hydrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure's scope as it can admit to other equally effective embodiments.

(2) FIG. 1A is a schematic of a conventional system for gasoline and aromatic production.

(3) FIG. 1B is a schematic of a conventional aromatics separation complex.

(4) FIG. 2 is a schematic of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a crude oil distillation unit for diesel hydrotreating.

(5) FIG. 3 is a schematic of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a diesel hydrotreating unit.

(6) FIG. 4 is a schematic of an embodiment of the present disclosure, in which aromatic bottoms are separated in a distillation column, where the fraction boiling within the diesel range is recycled back to a diesel hydrotreating unit.

(7) FIG. 5 is a schematic of an embodiment of the present disclosure, in which aromatic bottoms are separated in a distillation column, where the fraction boiling within the distillate range is recycled back to a kerosene hydrofinishing unit.

(8) FIG. 6 is a schematic of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a crude oil distillation column for kerosene hydrofinishing.

DETAILED DESCRIPTION

(9) So that the manner in which the features and advantages of the embodiments of systems and methods for gasoline and diesel recovery from aromatic complex bottoms, as well as others, which will become apparent, may be understood in more detail, a more particular description of the embodiments of the present disclosure briefly summarized previously may be had by reference to the embodiments thereof, which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the disclosure and are therefore not to be considered limiting of the present disclosure's scope, as it may include other effective embodiments as well.

(10) Referring first to FIG. 1A, a schematic of a conventional system for gasoline and aromatic production is shown. In the embodiment of FIG. 1A, a refinery with an aromatic complex is presented. In refining system 100, a crude oil inlet stream 102 is fluidly coupled to atmospheric distillation unit (ADU) 10, and crude oil from the crude oil inlet stream 102 is separated into naphtha stream 104, atmospheric residue stream 105, and diesel stream 106. Diesel stream 106 proceeds to diesel hydrotreating unit (DHT) 30, and naphtha stream 104 proceeds to naphtha hydrotreating unit (NHT) 20. A hydrotreated naphtha stream 108 exits NHT 20 and enters catalytic naphtha reforming unit (NREF) 40. A separated hydrogen stream 110 exits NREF 40, and a reformate stream 112 also exits NREF 40. A portion of reformate stream 112 enters aromatic complex (ARC) 50, and another portion of reformate stream 112 is separated by pool stream 114 to a gasoline pool. ARC 50 separates the reformate from reformate stream 112 into pool stream 116, aromatics stream 118, and aromatic bottoms 120.

(11) The crude oil is distilled in ADU 10 to recover naphtha, which boils in the range of about 36° C. to about 180° C., and diesel, which boils in the range of about 180° C. to about 370° C. An atmospheric residue fraction in atmospheric residue stream 105 boils at about 370° C. and higher. Naphtha stream 104 is hydrotreated in NHT 20 to reduce the sulfur and nitrogen content to less than about 0.5 ppmw, and the hydrotreated naphtha stream 108 is sent to NREF 40 to improve its quality, or in other words increase the octane number to produce gasoline blending stream or feedstock for an aromatics recovery unit. Diesel stream 106 is hydrotreated in DHT 30 to desulfurize the diesel oil to obtain a diesel fraction meeting stringent specifications at ultra-low sulfur diesel (ULSD) stream 121, such as, for example, less than 10 ppm sulfur. An atmospheric residue fraction is either used as a fuel oil component or sent to other separation or conversion units to convert low value hydrocarbons to high value products. Reformate stream 112 from NREF 40 can be used as a gasoline blending component or sent to an aromatic complex, such as ARC 50, to recover high value aromatics, such as benzene, toluene and xylenes.

(12) Referring now to FIG. 1B, a schematic of a prior art aromatics separation complex 122, such as, for example, ARC 50 of FIG. 1, is shown. Reformate stream 124 from a catalytic reforming unit, such as, for example, NREF 40 of FIG. 1, is split into two fractions: light reformate stream 128 with C.sub.5-C.sub.6 hydrocarbons, and heavy reformate stream 130 with C.sub.7+ hydrocarbons. A reformate splitter 126 separates reformate stream 124. The light reformate stream 128 is sent to a benzene extraction unit 132 to extract the benzene as benzene product in stream 138, and to recover substantially benzene-free gasoline in raffinate motor gasoline (mogas) stream 136. The heavy reformate stream 130 is sent to a splitter 134 which produces a C.sub.7 cut mogas stream 140 and a C.sub.8+ hydrocarbon stream 142.

(13) Still referring to FIG. 1B, a xylene rerun unit 144 separates C.sub.8+ hydrocarbons into C.sub.8 hydrocarbon stream 146 and C.sub.9+ (heavy aromatic mogas) hydrocarbon stream 148. C.sub.8 hydrocarbon stream 146 proceeds to p-xylene extraction unit 150 to recover p-xylene in p-xylene product stream 154. P-xylene extraction unit 150 also produces a C.sub.7 cut mogas stream 152, which combines with C.sub.7 cut mogas stream 140 to produce C.sub.7 cut mogas stream 168. Other xylenes are recovered and sent to xylene isomerization unit 158 by stream 156 to convert them to p-xylene. The isomerized xylenes are sent to splitter column 162. The converted fraction is recycled back to p-xylene extraction unit 150 from splitter column 162 by way of streams 164 and 146. Splitter top stream 166 is recycled back to reformate splitter 126. The heavy fraction from the xylene rerun unit 144 is recovered as process reject or aromatic bottoms (shown as C.sub.9+ and Hvy Aro MoGas in FIG. 1B at stream 148).

(14) Referring now to FIG. 2, a schematic is shown of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a crude oil distillation unit. In crude oil separation and upgrading system 200, crude oil stream 202 is combined with aromatic bottoms stream 232 to form hydrocarbon feed stream 204, which feeds ADU 206. ADU 206 separates hydrocarbons from hydrocarbon feed stream 204 into naphtha stream 208, atmospheric residue stream 209, and diesel stream 210. Diesel stream 210 is fed to DHT 212 for processing to produce ULSD stream 213. Naphtha stream 208 is fed to NHT 214 for processing. A hydrotreated naphtha stream 216 is fed to NREF 218. NREF 218 produces a hydrogen stream 220 and a reformate stream 222. A portion of reformate stream 222 proceeds to a gasoline pool by way of stream 224, and a portion of reformate stream 222 is fed to ARC 226. ARC 226 produces aromatics, for example benzene and xylenes, at stream 230 and aromatic bottoms at stream 232. A portion of hydrocarbons from ARC 226 goes to the gasoline pool by way of stream 228.

(15) As described herein, the term “aromatics” includes C.sub.6-C.sub.8 aromatics, such as for example benzene and xylenes, for example streams 138, 154 in FIG. 1B, whereas “aromatic bottoms” include the heavier fraction, for example stream 148 in FIG. 1B (C.sub.9+). Aromatic bottoms relate to C.sub.9+ aromatics and may be a more complex mixture of compounds including di-aromatics. C.sub.9+ aromatics boil in the range of about 100° C. to about 350° C.

(16) Aromatics bottoms at stream 232 are recycled to the ADU 206 for full extinction. Hydrocarbons boiling in the naphtha and diesel temperature range from the aromatic bottoms stream 232 and also from the crude oil stream 202 are recovered and processed in the processing units. Recycled aromatics bottoms at stream 232 will not substantially change the operating conditions, as the stream 232 is in the naphtha and gasoline boiling range. The liquid hourly space velocity (“LHSV”) may be impacted, as there will be increased feed to the respective naphtha and diesel units.

(17) Referring now to FIG. 3, a schematic is shown of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a diesel hydrotreating unit. In crude oil separation and upgrading system 300, crude oil stream 302 feeds ADU 304, which separates crude oil into naphtha stream 306, atmospheric residue stream 307, and diesel stream 308. Diesel stream 308 is combined with aromatic bottoms stream 332 to produce a diesel feed stream 310 to feed DHT 312 and produce ULSD stream 313. Naphtha stream 306 is fed to NHT 314 for processing. A hydrotreated naphtha stream 316 is fed to NREF 318. NREF 318 produces a hydrogen stream 320 and a reformate stream 322. A portion of reformate stream 322 proceeds to a gasoline pool by way of stream 324, and a portion of reformate stream 322 is fed to ARC 326. ARC 326 produces aromatics at stream 330 and aromatic bottoms at stream 332. The aromatic bottoms stream 332 is recycled to DHT 312 for full extinction. Aromatic bottoms are processed in the diesel hydrotreating unit 312 to increase the quality to be used as gasoline or diesel blending components. A portion of hydrocarbons from ARC 326 goes to the gasoline pool by way of stream 328.

(18) Referring now to FIG. 4, a schematic is shown of an embodiment of the present disclosure, in which aromatic bottoms are separated in a distillation column and the fraction boiling within the diesel range is recycled back to a diesel hydrotreating unit. In crude oil separation and upgrading system 400, crude oil stream 402 feeds ADU 404, which separates crude oil into naphtha stream 406, atmospheric residue stream 407, and diesel stream 408. Diesel stream 408 is combined with a stream of hydrocarbons boiling in the diesel range, diesel range stream 438, to produce a diesel feed stream 410 to feed DHT 412 and produce ULSD stream 413. Naphtha stream 406 is fed to NHT 414 for processing. A hydrotreated naphtha stream 416 is fed to NREF 418. NREF 418 produces a hydrogen stream 420 and a reformate stream 422. A portion of reformate stream 422 goes to a gasoline pool by way of stream 424, and a portion of reformate stream 422 is fed to ARC 426.

(19) ARC 426 produces aromatics at stream 430 and aromatic bottoms at stream 432. A portion of hydrocarbons from ARC 426 goes to the gasoline pool by way of stream 428. The aromatic bottoms stream 432 is sent to ADU 434 to produce a gasoline stream 436 and the hydrocarbons boiling in diesel range stream 438. Aromatic bottoms are processed in the diesel hydrotreating unit 412 to increase the quality to be used as gasoline or diesel blending components. Gasoline stream 436 includes tops, such as hydrocarbons boiling in the naphtha/gasoline range. Gasoline stream 436 has a good quality and can be used as a blending component without any further treatment. As noted, hydrocarbons boiling in diesel range stream 438 are recycled to DHT 412 to improve quality and to be used as a blending component.

(20) Referring now to FIG. 5, a schematic is shown of an embodiment of the present disclosure, in which aromatic bottoms are separated in a distillation column and the fraction boiling within the distillate range is recycled back to a kerosene hydrofinishing unit. In crude oil separation and upgrading system 500, Crude oil stream 502 feeds ADU 504, which separates crude oil into naphtha stream 506, atmospheric residue stream 507, and distillate stream 508. Naphtha from stream 506 and stream 514 are combined to form naphtha feed 518 for NHT 520. Distillate stream 508 is combined with heavy aromatics stream 542 to produce a distillate feed stream 510 to feed kerosene hydrofinishing unit (KHT) 512. A hydrotreated naphtha stream 522 is fed to NREF 524. NREF 524 produces a hydrogen stream 526 and a reformate stream 528. A portion of reformate stream 528 goes to a gasoline pool by way of stream 530, and a portion of reformate stream 528 is fed to ARC 532.

(21) ARC 532 produces aromatics at stream 536 and aromatic bottoms at stream 538. A portion of hydrocarbons from ARC 532 goes to the gasoline pool by way of stream 534. The aromatic bottoms stream 538 is sent to ADU 540 to produce a gasoline stream 541 and the heavy aromatics stream 542. Heavy aromatics stream 542 is processed in KHT 512 to increase the quality to be used as gasoline or diesel blending components. Gasoline stream 541 has a good quality and can be used as a blending component without any further treatment.

(22) KHT 512 includes a hydrotreating section and a cracking section with intermediate separation and a fractionation system. The first stage is a sour hydrotreating stage for processing distillate from the ADU 504. Stripped effluent is then mixed with heavy aromatics and is sent to a second stage which includes a sweet hydroprocessing stage including noble metal catalyst-based aromatic saturation and hydrocracking.

(23) One objective in KHT 512 is to produce kerosene that is essentially very low in aromatics and high in smoke point, which can be used as dual purpose kerosene for both heating and jet fuel requirements, the dual purpose kerosene exiting as stream 516. Operating Conditions of the first stage are similar to a conventional ultra-low sulfur diesel (ULSD) hydrotreating unit, while the sweet second stage would be combined with aromatic saturation kerosene hydrotreating (first stage LHSV 1-5 h.sup.−1; and a cracking section LHSV of 3-8 h.sup.−1). The system pressure, in some embodiments, is governed by the aromatic saturation requirement, or in other words the smoke point of kerosene as opposed to the hydrodesulfurization (HDS) requirement for ULSD.

(24) Referring now to FIG. 6, a schematic is shown of an embodiment of the present disclosure, in which aromatic bottoms are recycled back to a crude oil distillation unit. In crude oil separation and upgrading system 600, crude oil stream 602 is combined with aromatic bottoms stream 638 to form hydrocarbon feed stream 604, which feeds ADU 606. ADU 606 separates hydrocarbons from hydrocarbon feed stream 604 into atmospheric residue stream 607, naphtha stream 608, and distillate stream 610. Naphtha from stream 608 and stream 616 are combined to form naphtha feed 612 for NHT 618. Distillate stream 610 is fed to a kerosene hydrofinishing unit (KHT) 614. A hydrotreated naphtha stream 620 is fed to NREF 624. NREF 624 produces a hydrogen stream 626 and a reformate stream 628. A portion of reformate stream 628 goes to a gasoline pool by way of stream 630, and a portion of reformate stream 628 is fed to ARC 632.

(25) ARC 632 produces aromatics at stream 636 and aromatic bottoms at stream 638. A portion of hydrocarbons from ARC 632 goes to the gasoline pool by way of stream 634. The aromatic bottoms stream 638 is recycled to the ADU 606 for full extinction. Hydrocarbons boiling in the naphtha and distillate temperature range from the aromatic bottoms stream 638 and also from crude oil stream 602 are recovered and processed in the processing units. The distillate stream 610 is processed in KHT 614 to increase the quality to be used as gasoline or diesel blending components.

(26) KHT 614 includes a hydrotreating and a cracking section in a series flow with intermediate separation followed by a fractionation system. The kerosene produced is essentially very low in aromatics and high in smoke point and can be used as dual purpose kerosene for both heating and jet fuel requirements, the dual purpose kerosene exiting as stream 622.

Example 1

(27) The system depicted in FIG. 4 is illustrated in this example. 5.514 kg of aromatics bottoms fraction is distilled in lab scale true boiling point distillation columns with 15 or more theoretical plates using ASTM method D2892. 3.109 Kg (56.5 W %) of gasoline fraction boiling in the range of about 36° C. to about 180° C. and 2.396 Kg (43.5 W %) of residue stream boiling above 180° C. were recovered. The gasoline fraction was analyzed for its content and octane numbers.

(28) TABLE-US-00001 TABLE 1 Properties and composition of all streams from Example 1. In the tables, “NAP” refers to not applicable. Feedstock Tops Gasoline Bottoms Aromatic Initial Boiling Point Diesel Property Bottoms (IBP) - 180° C. 180+° C. Density 0.913 0.873 0.9226 Octane Number ASTM NAP 107 NAP D2699 Cetane Index ASTM NAP 16 D976 IBP 21 153 163 5 W % 36 161 178 10 W % 34 162 167 30 W % 58 163 196 50 W % 98 169 221 70 W % 138 171 258 90 W % 168 184 336 95 W % 181 184 338 FBP 207 251 351 Paraffins 0.17 Mono Aromatics 74.60 Naphthene Mono 3.06 Aromatics Diaromatics 15.36 Naphthene Di Aromatics 5.21 Tri Aromatics 0.59 Naphthene tri Aromatics 0.78 Tetra Aromatics 0.18 Naphthene tetra 0.15 Aromatics Penta Aromatics 0.42

(29) TABLE-US-00002 TABLE 2 Paraffins, isoparaffins, olefins, naphthenes, and aromatics (PIONA) of Gasoline Fraction (IBP - 180° C.). Fraction Component W % i-paraffins 3,3-Dimethylhexane 0.169 Mono-Aromatics i-Propylbenzene 0.794 n-Propylbenzene 4.377 1-Methyl-3-ethylbenzene 16.816 1-Methyl-4-ethylbenzene 7.729 1,3,5-Trimethylbenzene 6.460 1-Methyl-2-ethylbenzene 7.484 1,2,4-Trimethylbenzene 28.890 i-Butylbenzene 0.093 sec-Butylbenzene 0.108 1,2,3-Trimethylbenzene 6.294 1-Methyl-3-i-propylbenzene 0.397 1-Methyl-4-i-propylbenzene 0.124 1,3-Diethylbenzene 0.392 1-Methyl-3-n-propylbenzene 0.705 1-Methyl-4-n-propylbenzene 15.725 1,3-Dimethyl-5-ethylbenzene 0.749 1-Methyl-2-n-propylbenzene 0.210 1,4,Dimethyl-2-ethylbenzene 0.457 1,3-Dimethyl-4-ethylbenzene 0.341 1,2-Dimethyl-4-ethylbenzene 0.666 1-Ethyl-4-i-propylbenzene 0.106 1-Methyl-1-n-butylbenzene 0.082 Lndenes 2,3-Dihydroindene 0.831

(30) Surprisingly and unexpectedly, gasoline obtained from the aromatic bottoms is a good quality. In other words, the gasoline initial boiling point (IBP)—180° C. fraction has an octane number sufficiently high to be directed to the gasoline pool without further processing. However, in some embodiments, the diesel cetane index is very low. The diesel cetane index may increase marginally. However, considering its amount, it may not deteriorate the diesel quality, where high quality gas oils such as Arabian are processed.

(31) The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.

(32) One of ordinary skill in the art will understand that standard components such as pumps, compressors, temperature and pressure sensors, valves, and other components not shown in the drawings would be used in applications of the systems and methods of the present disclosure.

(33) In the drawings and specification, there have been disclosed example embodiments of the present disclosure, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments of the present disclosure have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure.