Patent Application
20180057758
The present disclosure relates to the production of petrochemical products and, more particularly, to systems and method for the direct production of petrochemical products from feedstock hydrocarbons.
Ethylene, propylene, butenes, butadiene, and aromatic compounds such as benzene, toluene, and xylene are basic intermediates for a large portion of the petrochemical industry. They are mainly obtained through the thermal cracking (sometimes referred to as “steam pyrolysis” or “steam cracking”) of petroleum gases and distillates such as naphtha, kerosene, or even gas oil. However, as demands rise for these basic intermediate compounds, other production sources must be considered beyond traditional thermal cracking processes utilizing petroleum gases and distillates as feedstocks.
These intermediate compounds may also be produced through refinery fluidized catalytic cracking (FCC) processes, where heavy feedstocks such as gas oils or residues are converted. For example, an important source for propylene production is refinery propylene from FCC units. However, the distillate feedstocks such as gas oils or residues are usually limited and result from several costly and energy intensive processing steps within a refinery.
Accordingly, in view of the ever growing demand of these intermediary petrochemical products, such as light olefins, there is a need for processes to produce these intermediate compounds from other types of feedstocks that are available in large quantities at relatively low cost. The present disclosure is related to processes and systems for producing these intermediate compounds, sometimes referred to in this disclosure as “system products,” by the direct conversion of feedstock hydrocarbons such as crude oil. For example, conversion from a crude oil feedstock may be beneficial as compared with other feedstocks in producing these intermediate compounds because it is generally less expensive and more widely available than other feedstock materials.
According to one or more embodiments, a feedstock hydrocarbon may be processed by a method which may comprise separating the feedstock hydrocarbon into a lesser boiling point hydrocarbon fraction and a greater boiling point hydrocarbon fraction, cracking the greater boiling point hydrocarbon fraction in a high-severity fluid catalytic cracking reactor unit to form a catalytically cracked effluent, cracking the lesser boiling point hydrocarbon fraction in a steam cracker unit to form a steam cracked effluent, and separating one or both of the catalytically cracked effluent or the steam cracked effluent to form two or more petrochemical products. In one or more embodiments, the feedstock hydrocarbon may comprise crude oil and one of the petrochemical products may comprise one or more light olefins.
According to another embodiment, a feedstock hydrocarbon may be processed by a method comprising introducing a feedstock hydrocarbon stream to a feedstock hydrocarbon separator that separates the feedstock hydrocarbon into a lesser boiling point hydrocarbon fraction stream and a greater boiling point hydrocarbon fraction stream, passing the greater boiling point hydrocarbon fraction stream to a high-severity fluid catalytic cracking reactor unit that cracks the greater boiling point hydrocarbon fraction stream to form a catalytically cracked effluent stream, passing the lesser boiling point hydrocarbon fraction stream to a steam cracker unit that cracks the lesser boiling point hydrocarbon fraction stream to form a steam cracked effluent stream, and separating one or both of the catalytically cracked effluent stream or the steam cracked effluent stream to form two or more petrochemical product streams.
Additional features and advantages of the technology described in this disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the technology as described in this disclosure, including the detailed description which follows, the claims, as well as the appended drawings.
The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
For the purpose of describing the simplified schematic illustrations and descriptions of
It should further be noted that arrows in the drawings refer to process streams. However, the arrows may equivalently refer to transfer lines which may serve to transfer process steams between two or more system components. Additionally, arrows that connect to system components define inlets or outlets in each given system component. The arrow direction corresponds generally with the major direction of movement of the materials of the stream contained within the physical transfer line signified by the arrow. Furthermore, arrows which do not connect two or more system components signify a product stream which exits the depicted system or a system inlet stream which enters the depicted system. Product streams may be further processed in accompanying chemical processing systems or may be commercialized as end products. System inlet streams may be streams transferred from accompanying chemical processing systems or may be non-processed feedstock streams. Some arrows may represent recycle streams, which are effluent streams of system components that are recycled back into the system. However, it should be understood that any represented recycle stream, in some embodiments, may be replaced by a system inlet stream of the same material, and that a portion of a recycle stream may exit the system as a system product.
Additionally, arrows in the drawings may schematically depict process steps of transporting a stream from one system component to another system component. For example, an arrow from one system component pointing to another system component may represent “passing” a system component effluent to another system component, which may include the contents of a process stream “exiting” or being “removed” from one system component and “introducing” the contents of that product stream to another system component.
It should be understood that two or more process streams are “mixed” or “combined” when two or more lines intersect in the schematic flow diagrams of
Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.
Described in this disclosure are various embodiments of systems and methods for processing feedstock hydrocarbons, such as crude oil, into petrochemical products such as light olefins. Generally, the processing of the feedstock hydrocarbon may include separating crude oil into a lesser boiling point hydrocarbon fraction and a greater boiling point hydrocarbon fraction, and then processing the greater boiling point hydrocarbon fraction in a high-severity fluid catalytic cracking (HS-FCC) reaction and processing the lesser boiling point hydrocarbon fraction in a stream cracking reaction. The products of the HS-FCC reaction and the steam cracking reaction may be further separated into desired petrochemical product streams. For example, crude oil may be utilized as a feedstock hydrocarbon and be directly processed into one or more of hydrocarbon oil, gasoline, mixed butenes, butadiene, propene, ethylene, methane, hydrogen, mixed C4, naphtha, and liquid petroleum gas.
As used in this disclosure, a “reactor” refers to a vessel in which one or more chemical reactions may occur between one or more reactants optionally in the presence of one or more catalysts. For example, a reactor may include a tank or tubular reactor configured to operate as a batch reactor, a continuous stirred-tank reactor (CSTR), or a plug flow reactor. Example reactors include packed bed reactors such as fixed bed reactors, and fluidized bed reactors. One or more “reaction zones” may be disposed in a reactor. As used in this disclosure, a “reaction zone” refers to an area where a particular reaction takes place in a reactor. For example, a packed bed reactor with multiple catalyst beds may have multiple reaction zones, where each reaction zone is defined by the area of each catalyst bed.
As used in this disclosure, a “separation unit” refers to any separation device that at least partially separates one or more chemicals that are mixed in a process stream from one another. For example, a separation unit may selectively separate differing chemical species from one another, forming one or more chemical fractions. Examples of separation units include, without limitation, distillation columns, flash drums, knock-out drums, knock-out pots, centrifuges, filtration devices, traps, scrubbers, expansion devices, membranes, solvent extraction devices, and the like. It should be understood that separation processes described in this disclosure may not completely separate all of one chemical consistent from all of another chemical constituent. It should be understood that the separation processes described in this disclosure “at least partially” separate different chemical components from one another, and that even if not explicitly stated, it should be understood that separation may include only partial separation. As used in this disclosure, one or more chemical constituents may be “separated” from a process stream to form a new process stream. Generally, a process stream may enter a separation unit and be divided, or separated, into two or more process streams of desired composition. Further, in some separation processes, a “lesser boiling point fraction” (sometimes referred to as a “light fraction”) and a “greater boiling point fraction” (sometimes referred to as a “heavy fraction”) may exit the separation unit, where, on average, the contents of the lesser boiling point fraction stream have a lesser boiling point than the greater boiling point fraction stream. Other streams may fall between the lesser boiling point fraction and the greater boiling point fraction, such as an “intermediate boiling point fraction.”
It should be understood that an “effluent” generally refers to a stream that exits a system component such as a separation unit, a reactor, or reaction zone, following a particular reaction or separation, and generally has a different composition (at least proportionally) than the stream that entered the separation unit, reactor, or reaction zone.
As used in this disclosure, a “catalyst” refers to any substance which increases the rate of a specific chemical reaction. Catalysts described in this disclosure may be utilized to promote various reactions, such as, but not limited to, cracking (including aromatic cracking), demetalization, dearomatization, desulfurization, and, denitrogenation. As used in this disclosure, “cracking” generally refers to a chemical reaction where a molecule having carbon to carbon bonds is broken into more than one molecule by the breaking of one or more of the carbon to carbon bonds, or is converted from a compound which includes a cyclic moiety, such as an aromatic, to a compound which does not include a cyclic moiety or contains fewer cyclic moieties than prior to cracking.
It should further be understood that streams may be named for the components of the stream, and the component for which the stream is named may be the major component of the stream (such as comprising from 50 weight percent (wt. %), from 70 wt. %, from 90 wt. %, from 95 wt. %, from 99 wt. %, from 99.5 wt. %, or even from 99.9 wt. % of the contents of the stream to 100 wt. % of the contents of the stream). It should also be understood that components of a stream are disclosed as passing from one system component to another when a stream comprising that component is disclosed as passing from that system component to another. For example, a disclosed “hydrogen stream” passing from a first system component to a second system component should be understood to equivalently disclose “hydrogen” passing from a first system component to a second system component.
Now referring to
Still referring to
Following the separation of the feedstock hydrocarbon stream 101 into the lesser boiling point hydrocarbon fraction stream 103 and the greater boiling point hydrocarbon fraction stream 104, the lesser boiling point hydrocarbon fraction stream 103 may be passed to a steam cracker unit 148. The steam cracker unit 148 may include a convection zone 150 and a pyrolysis zone 151. The lesser boiling point hydrocarbon fraction stream 103 may pass into the convection zone 150 along with steam 105. In the convection zone 150, the lesser boiling point hydrocarbon fraction stream 103 may be pre-heated to a desired temperature, such as from 400° C. to 650° C. The contents of the lesser boiling point hydrocarbon fraction stream 103 present in the convection zone 150 may then be passed to the pyrolysis zone 151 where it is steam-cracked. The steam-cracked effluent stream 107 may exit the steam cracker unit 148 and be passed through a heat exchanger 108 where process fluid 109, such as water or pyrolysis hydrocarbon oil, cools the steam-cracked effluent stream 107 to form the cooled steam-cracked effluent stream 110. The steam-cracked effluent stream 107 and cooled steam-cracked effluent stream 110 may include a mixture of cracked hydrocarbon-based materials which may be separated into one or more petrochemical products included in one or more system product streams. For example, the steam-cracked effluent stream 107 and the cooled steam-cracked effluent stream 110 may include one or more of hydrocarbon oil, gasoline, mixed butenes, butadiene, propene, ethylene, methane, and hydrogen, which may further be mixed with water from the stream cracking.
According to one or more embodiments, the pyrolysis zone 151 may operate at a temperature of from 700° C. to 900° C. The pyrolysis zone 151 may operate with a residence time of from 0.05 seconds to 2 seconds. The mass ratio of steam 105 to lesser boiling point hydrocarbon fraction stream 103 may be from about 0.3:1 to about 2:1.
The greater boiling point hydrocarbon fraction stream 104 may exit the feedstock hydrocarbon separator 102 and be combined with a hydrogen stream 153 to form a mixed stream 123. The hydrogen stream 153 may be supplied from a source outside of the system, such as feed hydrogen stream 122, or may be supplied from a system recycle stream, such as purified hydrogen stream 121. In another embodiment, the hydrogen stream 153 may be from a combination of sources such as partially being supplied from feed hydrogen stream 122 and partially supplied from purified hydrogen stream 121. The volumetric ratio of components from the hydrogen stream 153 to components of the greater boiling point hydrocarbon fraction stream 104 present in the mixed stream 123 may be from 400:1 to 1500:1, and may depend on the contents of the greater boiling point hydrocarbon fraction stream 104.
The mixed stream 123 may then be introduced to a hydroprocessing unit 124. The hydroprocessing unit 124 may at least partially reduce the content of metals, nitrogen, sulfur, and aromatic moieties. For example, the hydroprocessed effluent stream 125 which exits the hydroprocessing unit 124 may have reduced content of one or more of metals, nitrogen, sulfur, and aromatic moieties by at least 2%, at least 5%, at least 10%, at least 25%, at least 50%, or even at least 75%. For example, a hydrodemetalization (HDM) catalyst may remove a portion of one or more metals from a process stream, a hydrodenitrogenation (HDN) catalyst may remove a portion of the nitrogen present in a process stream, and a hydrodesulfurization (HDS) catalyst may remove a portion of the sulfur present in a process stream. Additionally, a hydrodearomatization (HDA) catalyst may reduce the amount of aromatic moieties in a process stream by saturating and cracking those aromatic moieties. It should be understood that a particular catalyst is not necessarily limited in functionality to the removal or cracking of a particular chemical constituent or moiety when it is referred to as having a particular functionality. For example, a catalyst identified in this disclosure as an HDN catalyst may additionally provide HDA functionality, HDS functionality, or both.
According to one or more embodiments, the hydroprocessing unit 124 may include multiple catalyst beds arranged in series. For example, the hydroprocessing unit 124 may comprise one or more of a hydrocracking catalyst, a hydrodemetalization catalyst, a hydrodesulfurization catalyst, and a hydrodenitrogenation catalyst, arranged in series. The catalysts of the hydroprocessing unit 124 may comprise one or more IUPAC Group 6, Group 9, or Group 10 metal catalysts such as, but not limited to, molybdenum, nickel, cobalt, and tungsten, supported on a porous alumina or zeolite support. As used in this disclosure, the hydroprocessing unit 124 serves to at least partially reduce the content of metals, nitrogen, sulfur, and aromatic moieties in the mixed stream 123, and should not be limited by the materials utilized as catalysts in the hydroprocessing unit 124. According to one embodiment, one or more catalysts utilized to reduce sulfur, nitrogen, and metals content may be positioned upstream of a catalyst which is utilized to hydrogenate or crack the reactant stream. According to one or more embodiments, the hydroprocessing unit 124 may operate at a temperature of from 300° C. to 450° C. and at a pressure of from 30 bars to 180 bars. The hydroprocessing unit 124 may operate with a liquid hour space velocity of from 0.3/hour to 10/hour.
According to one or more embodiments, the contents of the stream entering the hydroprocessing unit 124 may have a relatively large amount of one or more of metals (for example, Vanadium, Nickel, or both), sulfur, and nitrogen. For example, the contents of the stream entering the hydroprocessing unit may comprise one or more of greater than 17 parts per million by weight of metals, greater than 135 parts per million by weight of sulfur, and greater than 50 parts per million by weight of nitrogen. The contents of the stream exiting the hydroprocessing unit 124 may have a relatively small amount of one or more of metals (for example, Vanadium, Nickel, or both), sulfur, and nitrogen. For example, the contents of the stream exiting the hydroprocessing unit may comprise one or more of 17 parts per million by weight of metals or less, 135 parts per million by weight of sulfur or less, and 50 parts per million by weight of nitrogen or less.
The hydroprocessed effluent stream 125 may exit the hydroprocessing unit 124 and be passed to a high-severity fluid catalytic cracking reactor unit 149. The high-severity fluid catalytic cracking reactor unit 149 may include a catalyst/feed mixing zone 126, a down flow reaction zone 127, a separation zone 128, and a catalyst regeneration zone 130. The hydroprocessed effluent stream 125 may be introduced to the catalyst/feed mixing zone 126 where it is mixed with regenerated catalyst from regenerated catalyst stream 129 passed from the catalyst regeneration zone 130. The hydroprocessed effluent stream 125 is reacted by contact with the regenerated catalyst in the reaction zone 127, which cracks the contents of the hydroprocessed effluent stream 125. Following the cracking reaction in the reaction zone 127, the contents of the reaction zone 127 are passed to the separation zone 128 where the cracked product of the reaction zone 127 is separated from spent catalyst, which is passed in a spent catalyst stream 131 to the catalyst regeneration zone 130 where it is regenerated by, for example, removing coke from the spent catalyst.
It should be understood that high-severity fluid catalytic cracking reactor unit 149 is a simplified schematic of one particular embodiment of a high-severity fluid catalytic cracking reactor unit, and other configurations of high-severity fluid catalytic cracking reactor units may be suitable for incorporation into the hydrocarbon conversion system 100. However, the high-severity fluid catalytic cracking reactor unit 149 may generally be defined by its incorporation of fluidized catalyst contacting the reactant at an elevated temperature of, for example, at least 500° C. According to one or more embodiments, the reaction zone 127 of the high-severity fluid catalytic cracking reactor unit 149 may operate at a temperature of from 530° C. to 700° C. with a weight ratio of catalyst to contents of the hydroprocessed effluent stream 125 of 10 wt. % to 40 wt. %. The residence time of the mixture in the reaction zone 127 may be from 0.2 to 2 seconds. A variety of fluid catalytic cracking catalysts may be suitable for the reactions of the high-severity fluid catalytic cracking reactor unit 149. For example, some suitable fluid catalytic cracking catalysts may include, without limitation, zeolites, silica-alumina, carbon monoxide burning promoter additives, bottoms cracking additives, light olefin-producing additives, and other catalyst additives used in the FCC processes. Example of cracking zeolites suitable for use in the high-severity fluid catalytic cracking reactor unit 149 include Y, REY, USY, and RE-USY zeolites. For enhanced light olefins production from naphtha cracking, ZSM-5 zeolite crystal or other pentasil type catalyst structure may be used.
The catalytically-cracked effluent stream 132 may exit the separation zone 128 of the high-severity fluid catalytic cracking reactor unit 149 and be combined with the cooled steam-cracked effluent stream 110, which was processed by the steam cracker unit 148. The combined stream containing the cooled steam-cracked effluent stream 110 and the catalytically-cracked effluent stream 132 may be separated by separation unit 111 into system product streams. For example, the separation unit 111 may be a distillation column which separates the contents of the cooled steam-cracked effluent stream 110 and the catalytically-cracked effluent stream 132 into one or more of a hydrocarbon oil stream 112, a gasoline stream 113, a mixed butenes stream 114, a butadiene stream 115, a propene stream 116, an ethylene stream 117, a methane stream 118, and a hydrogen stream 119. The cooled steam-cracked effluent stream 110 may be mixed with the catalytically-cracked effluent stream 132 prior to introduction to the separation unit 111 as depicted in
As depicted in
Now referring to
The liquefied petroleum gas stream 138 may exit the cracking reactor separator 133 and be combined with the cooled steam-cracked effluent stream 110. The combined stream containing the cooled steam-cracked effluent stream 110 and the liquefied petroleum gas stream 138 may be separated by a separation unit 111 into system product streams. For example, similar to the embodiment of
Now referring to
In the embodiments where the greater boiling point hydrocarbon fraction stream 104 is not hydroprocessed to reduce nitrogen, sulfur, aromatics, metals, and combinations of such, the greater boiling point hydrocarbon fraction stream 104 may be introduced to the high-severity fluid catalytic cracking reactor unit 149 comprising a composition having one or more of greater than 17 parts per million by weight of metals, greater than 135 parts per million by weight of sulfur, and greater than 50 parts per million by weight of nitrogen.
Furthermore, it should be understood that the embodiment of
According to the embodiments disclosed with reference to
According to another embodiment, capital costs may be reduced by the designs of the hydrocarbon conversion systems 100, 200, 300 of
According to another embodiment, system components such as vapor-solid separation devices and vapor-liquid separation devices may not need to be utilized between the convection zone 150 and the pyrolysis zone 151 of the steam cracker unit 148. In some conventional steam cracker units, a vapor-liquid separation device may be required to be positioned between the convection zone and the pyrolysis zone. This vapor-liquid separation device may be used to remove the greater boiling point components present in a convection zone, such as any vacuum residues. However, in some embodiments of the hydrocarbon conversion systems 100, 200, 300 of
The various embodiments of methods and systems for the conversion of a feedstock hydrocarbons will be further clarified by the following examples. The examples are illustrative in nature, and should not be understood to limit the subject matter of the present disclosure.
Product yields were determined by experimentation with a steam cracker pilot plant utilizing a hydroprocessed Arab light crude oil as feedstock. Table 2A shows the Arab light crude oil utilized as the feedstock before and after hydroprocessing. The hydroprocessed Arab light crude oil was pre-cut at 540° C. to remove greater boiling point fractions from the feedstock to simulate the effect of a vapor-liquid separation device utilized in conventional steam cracker units between the convection zone and the pyrolysis zone. A cracking severity of 840° C. coil outlet temperature was used for testing. The product yields for Comparative Example A are shown in Table 2B.
Product yields were computer modeled for the reactor systems depicted in
Product yields were modeled for the reactor systems depicted in
It is noted that one or more of the following claims utilize the term “where” as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”
It should be understood that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure.
Having described the subject matter of the present disclosure in detail and by reference to specific embodiments, it is noted that the various details described in this disclosure should not be taken to imply that these details relate to elements that are essential components of the various embodiments described in this disclosure, even in cases where a particular element is illustrated in each of the drawings that accompany the present description. Rather, the claims appended hereto should be taken as the sole representation of the breadth of the present disclosure and the corresponding scope of the various embodiments described in this disclosure. Further, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims.
This application claims benefit to U.S. Provisional Application 62/378,988 filed Aug. 24, 2016, which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62378988 | Aug 2016 | US |
