Method for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products

Abstract

A process for converting hydrocarbons originating from refinery operations such as atmospheric distillation unit or a fluid catalytic cracking unit (FCC), into lighter boiling hydrocracked hydrocarbons having a boiling point lower than naphthalene and lower.

Claims

1. A process for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products, said lighter boiling hydrocarbon products being suitable as a feedstock for petrochemicals processes, said converting process comprising the steps of: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking units, wherein the cascade of hydrocracking units comprises at least two hydrocracking units; cracking said heavy hydrocarbon feedstock in one of the hydrocracking units to produce a cracked feedstock; separating said cracked feedstock into a top stream comprising a light boiling hydrocarbon fraction and a bottom stream comprising a heavy hydrocarbon fraction; feeding the entire said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein the process conditions in each hydrocracking unit are different from each other, in which the temperature from the first to the subsequent hydrocracking units increases; processing lighter boiling hydrocarbon fractions from each hydrocracking unit as a feedstock for a BTX and LPG producing unit, said BTX and LPG producing unit being a hydrocracking unit wherein the process conditions prevailing in said hydrocracking unit are different from the process conditions prevailing in any one of the hydrocracking units in the cascade of hydrocracking units; wherein the lighter boiling hydrocarbon fractions from all hydrocracking units in said cascade of hydrocracking units are hydrocarbons having a boiling point lower than naphthalene; and wherein each hydrocracking unit in said cascade of hydrocracking units is operated under liquid phase hydrocracking conditions, and wherein said hydrocracking unit as said BTX and LPG producing unit is operated under gaseous phase hydrocracking conditions.

2. The process according to claim 1, wherein the lighter boiling hydrocarbon fractions from said hydrocracking unit are sent to a separation section, in which section a fraction comprising C5 material is separated from said lighter boiling hydrocarbon fractions, and the remaining part of said lighter boiling hydrocarbon fractions is processed as a feedstock for said BTX and LPG producing unit.

3. The process according claim 2, further comprising processing said C5 material in dehydrogenation units by further pre-separating said C5 material into a stream comprising C3 and a stream comprising C4 and feeding said streams to a propane dehydrogenation unit and a butane dehydrogenation unit, respectively.

4. The process according to claim 1, further comprising separating hydrogen from said lighter boiling hydrocarbon fractions and feeding said hydrogen thus separated to at least one of a hydrocracking unit in said cascade of hydrocracking unit, a preceding hydrocracker unit in said cascade of hydrocracking unit, and to said BTX and LPG producing unit.

5. The process according to claim 1, further comprising processing a fraction comprising LPG as produced in said LPG producing unit as a feedstock for one or more process units including at least one of a steam cracking unit, an aromatization unit, a propane dehydrogenation unit, a butane dehydrogenation unit and a mixed propane-butane dehydrogenation unit.

6. The process according to claim 1, wherein said hydrocracking units are preceded by a hydrotreating unit, wherein the bottom stream of said hydrotreating unit is used as a feedstock for said first hydrocracking unit, and the temperature prevailing in said hydrotreating unit is higher than in said first hydrocracking unit.

7. The process according to claim 1, wherein the temperature in the first hydrocracking unit is lower than the temperature in the second hydrocracking unit, and wherein particle size of the catalyst present in the cascade of hydrocracking units decreases from the first hydrocracking unit to the subsequent hydrocracking unit.

8. The process according to claim 6, wherein the temperature in the cascade of hydrocracking units increases, and wherein the temperature prevailing in said second hydrocracking unit is higher than in said hydrotreating unit.

9. The process according to claim 1, wherein the reactor type design of the hydrocracking unit includes at least one of a fixed bed type, ebulated bed reactor type and a slurry phase type, wherein the reactor type design of said hydrotreating unit is of the fixed bed type, wherein the reactor type design of said first hydrocracking unit is of the ebulated bed reactor type, and wherein the reactor type design of said second hydrocracking unit is of the slurry phase type.

10. A process for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products, said lighter boiling hydrocarbon products being suitable as a feedstock for petrochemicals processes, said converting process comprising the steps of: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking units, wherein the cascade of hydrocracking units comprises at least two hydrocracking units; cracking said heavy hydrocarbon feedstock in one of the hydrocracking unit to produce a cracked feedstock; separating said cracked feedstock into a top stream comprising a light boiling hydrocarbon fraction and a bottom stream comprising a heavy hydrocarbon fraction; feeding the entire said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein the process conditions in each hydrocracking unit are different from each other, in which the temperature from the first to the subsequent hydrocracking units increases; processing lighter boiling hydrocarbon fractions from each hydrocracking unit as a feedstock for a BTX and LPG producing unit, said BTX and LPG producing unit being a hydrocracking unit wherein the process conditions prevailing in said hydrocracking unit are different from the process conditions prevailing in any one of the hydrocracking units in the cascade of hydrocracking units, and wherein the lighter boiling hydrocarbon fractions from all hydrocracking units in said cascade of hydrocracking units are hydrocarbons having a boiling point lower than naphthalene.

11. A process for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products, said lighter boiling hydrocarbon products being suitable as a feedstock for petrochemicals processes, said converting process comprising the steps of: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking units, wherein the cascade of hydrocracking units comprises at least two hydrocracking units; cracking said heavy hydrocarbon feedstock in one of the hydrocracking unit to produce a cracked feedstock; separating said cracked feedstock into a top stream comprising a light boiling hydrocarbon fraction and a bottom stream comprising a heavy hydrocarbon fraction; feeding said bottom stream of such a hydrocracking unit as a feedstock directly to a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein the process conditions in each hydrocracking unit is different from each other, in which the temperature from the first to the subsequent hydrocracking units increases; processing lighter boiling hydrocarbon fractions from each hydrocracking unit as a feedstock for a BTX and LPG producing unit, said BTX and LPG producing unit being a hydrocracking unit wherein the process conditions prevailing in said hydrocracking unit are different from the process conditions prevailing in any one of the hydrocracking units in the cascade of hydrocracking units.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in further detail below and in conjunction with the attached drawings in which the same or similar elements are referred to by the same number.

(2) FIG. 1 is a schematic illustration of an embodiment of the process of the invention.

(3) FIG. 2 is a schematic illustration of another embodiment of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now to the process and apparatus 1 schematically depicted in FIG. 1, there is shown crude oil feed 1, an atmospheric distillation unit 2 for separating the crude oil into stream 29, comprising hydrocarbons having a boiling point lower than naphthalene. Bottom stream 3 leaving distillation unit 2 is fed to a hydro processing unit 4, for example a hydro treating unit, wherein the thus treated hydrocarbons 5 are sent to a separation unit 6 producing a gaseous stream 7 and a bottom stream 13 comprising hydrocarbons having a boiling point of naphthalene and higher. Stream 7 is further separated in separation unit 8 into a stream 9 comprising hydrogen and a bottom stream 12 comprising hydrocarbons having a boiling point lower than naphthalene. Stream 13 is fed into a hydrocracking unit 15 and its effluent 16 is sent to a separation unit 17 producing gaseous stream 18 and a bottom stream 20 comprising hydrocarbons having a boiling point of naphthalene and higher. Stream 18 is further separated in separation unit 19 into stream 14, comprising hydrogen and a stream 21, comprising hydrocarbons having a boiling point lower than naphthalene. Hydrogen make up is indicated with reference number 10. The effluent 20 from separation unit 17 is sent to a further hydrocracking unit 22 and its effluent 23 is sent to a separation unit 24 producing a top stream 44 and a bottom stream 27. Top stream 44 is further separated in separation unit 38 into stream 26 comprising hydrogen and a bottom stream 28 comprising hydrocarbons having a boiling point lower than naphthalene. The hydrogen containing stream leaving separation unit 38 is sent to compressor 11 and returned to the inlet of hydrocracking unit 22. The same recycle of hydrogen applies for streams 9, 14. The top stream coming from distillation unit 2 and streams 12, 21 and 28 are combined as a stream 29, which stream 29 is directly sent to a hydrocracker 30. Processing the full stream 29 via unit 30 without any separation is sensible if only a small amount of LPG already exists in stream 29 as this will reduce the number of processing units (and thus costs) without greatly increasing the size etc. of hydrocracker unit 30.

(5) According to a preferred embodiment it is also possible to separate stream 29 in separation unit 60 into a C5 portion (stream 61) and a C6+ portion (stream 62), and to process the C6+ portion via unit 30 to make pure BTX and to convert any C6+ non-aromatics into LPG species. In parallel, process the C5 portion via some other units (not specified) for which this is a good feed.

(6) According to another preferred embodiment it is also possible to separate stream 29 into a C4 portion (LPG) (stream 61), and a C5+ portion (stream 62), and to process the C5+ portion (stream 62), via unit 30 to make pure BTX and to convert any C5+ non-aromatics into LPG species. In parallel, process the C4 portion (stream 61, potentially in combination with the LPG product from unit 30, i.e. stream 36, via some other units e.g. propane/butane dehydrogenation units.

(7) Effluent 31 from hydrocracking unit 30 is sent to a separation unit 32 producing a top stream 33 and a bottom stream 35, mainly comprising BTX. Top stream 33 is further separated in separation unit 34 into stream 36, comprising LPG, and a top stream 37, comprising hydrogen. Stream 37 is recycled to the inlet of hydrocracking unit 30.

(8) According to FIG. 2 the process and apparatus are identified with reference number 2, wherein crude oil 1 is sent to a distillation unit 2 and separated into a top stream 29 and a bottom stream 3. Bottom stream 3 is sent to a hydrocracking unit 4, especially a hydro treating unit, producing effluent 5. Effluent 5 is sent to a separation unit 6 producing a top stream 7 and a bottom stream 13, comprising hydrocarbons having a boiling point of naphthalene and higher. Top stream 7 is further separated in separation unit 8 into top stream 40, mainly comprising hydrogen and bottom stream 12, comprising hydrocarbons having a boiling point lower than naphthalene. Stream 13 is sent to a first hydrocracking unit 15 producing effluent stream 16. Effluent stream 16 is sent to a separation unit 17 producing a top stream 18 and a bottom stream 20. Stream 18 is further separated in separation unit 19 producing stream 43, comprising hydrogen. Stream 43 is in FIG. 2 recycled to the inlet of hydrocracking unit 4. The bottom stream 21 of separation unit 19 is combined with top stream 29 from unit 2 and sent to hydrocracking unit 30.

(9) Processing the full stream 29 via unit 30 without any separation is sensible if only a small amount of LPG already exists in stream 29 as this will reduce the number of processing units (and thus costs) without greatly increasing the size etc. of hydrocracker unit 30.

(10) According to a preferred embodiment it is also possible to separate stream 29, before entering unit 30, into a C5 portion (stream 61), and a C6+ portion (stream 62), and to process the C6+ portion (stream 62), via unit 30 to make pure BTX and to convert any C6+ non-aromatics into LPG species. In parallel, process the C5 portion (stream 61) via some other units (not specified) for which this is a good feed.

(11) According to another preferred embodiment it is also possible to separate stream 29, before entering unit 30, into a C4 portion (stream 61) (LPG) and a C5+ portion (stream 62) and to process the C5+ portion (stream 62) via unit 30 to make pure BTX and to convert any C5+ non-aromatics into LPG species. In parallel, process the C4 portion (stream 62, potentially in combination with the LPG product from unit 30, i.e. stream 36) via some other units e.g. (propane/butane dehydrogenation units).

(12) Bottom stream 20 from separation unit 17 is sent to a second hydrocracking unit 22 producing effluent 23. Effluent 23 is further separated in separation column 24 into a top stream 45 and a bottom stream 27, qualified as heavy pitch. A portion of stream 27 is recycled as stream 25 to the inlet of second hydrocracking unit 22. In separation column 38 top stream 45 is further separated into top stream 42, mainly comprising hydrogen, and bottom stream 28, mainly comprising hydrocarbons having a boiling point less than the boiling point of naphthalene. The hydrogen containing stream 42 is recycled to the inlet of hydrocracking unit 15. Top stream 40 leaving separation column 8 is combined with hydrogen make up 10 and forms a stream 41 as an inlet stream for hydrocracking unit 30. Effluent 31 coming from hydrocracking unit 30 is further separated in separation unit 32 into a top stream 33 and a bottom stream 35, comprising BTX. Top stream 33 is further separated in separation column 34 into stream 36, mainly comprising LPG.

(13) According to another embodiment it is preferred to redesign units 30, 32 and 33 to convert the aromatic and naphthenic the species in stream 29 (including the material from streams 12, 21 and 28) into LPG. This embodiment can be identified as an indirect route as each hydrocracker unit in the cascade makes some LPG material but also other species which are converted to LPG in a second hydrocracker. This would mean operating hydrocracking unit 30 at a lower temperature and higher hydrogen partial pressure. There is a change in the distillation section of this facility as one could either eliminate column 32 (as there is no BTX product stream 35) or use column 32 as a way of recycling material heavier than LPG (stream 35) back to the reactor (unit 30). In this way of operating one could continue to operate the reactors and separation systems for the other hydrocrackers as previously described.