Abstract:
Methods and oil refinery apparatuses are provided for producing hydrocarbons. A method includes fractionating a crude oil feedstock to produce a crude saturated stream and a residual stream. The residual stream is cracked in a cracking device to produce an unsaturated stream, and the unsaturated stream and the crude saturated stream are combined to produce a combined stream. The combined stream is fractionated to produce a refinery fuel gas stream.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to methods and apparatuses for producing hydrocarbons, and more particularly relates to methods and apparatuses for producing hydrocarbons with limited refinery equipment to reduce cost. 
       BACKGROUND 
       [0002]    Crude oil is produced and processed in oil refineries all over the world. Crude oil includes a mixture of hydrocarbons with a wide variety of molecular weights, sulfur compounds, nitrogen compounds, and other compounds. Oil refining apparatuses separate the different compounds to produce various products, and many of these products are further processed. For example, sulfur compounds may be removed and hydrocarbons that boil within a prescribed range may be isolated for use as fuel. Specific hydrocarbons, such as para-xylene, may be produced and/or separated. Some process streams are further processed to produce compounds with a higher value or more demand, such as the cracking of heavy oils to produce diesel fuels or gasoline with high cetane or octane ratings, respectively. The refining of crude oil is an important component of the world economy. 
         [0003]    Oil refining apparatuses typically include many different process units connected together, where the process units may be sized for large scale production. As such, oil refining apparatuses are expensive to build and operate. The cost to build and operate an oil refining apparatus can be prohibitive. Therefore, there is a need for oil refinery configurations that reduce the equipment count and thereby reduce the installation and operating costs of oil refinery apparatuses. 
         [0004]    Accordingly, it is desirable to develop methods and oil refining apparatuses for producing hydrocarbons from crude oil that co-process similar streams. In addition, it is desirable to develop methods and oil refining apparatuses for producing hydrocarbons with reduced equipment counts over traditional oil refinery configurations. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       BRIEF SUMMARY 
       [0005]    Oil refining apparatuses and methods of producing hydrocarbons are provided. In an exemplary embodiment, a method includes fractionating a crude oil feedstock to produce a crude saturated stream and a residual stream. The residual stream is cracked in a cracking device to produce an unsaturated stream, and the unsaturated stream and the crude saturated stream are combined to produce a combined stream. The combined stream is fractionated to produce a refinery fuel gas stream. 
         [0006]    In accordance with another exemplary embodiment, a method for producing hydrocarbons includes hydrocracking a hydrocracker feedstock to produce a hydrocracker saturated stream and a hydrocracker product stream. A residual stream is cracked in a cracking device to produce an unsaturated stream. The hydrocracker saturated stream and the unsaturated stream are combined to produce a combined stream, and the combined stream is fractionated to produce a gasoline stream. 
         [0007]    In accordance with a further exemplary embodiment, an oil refining apparatus includes a crude distillation unit with a crude receiver. A saturated compressor is fluidly coupled to the crude receiver, and a fluid catalytic cracking unit is fluidly coupled to the crude distillation unit. A fluid catalytic cracking compressor is fluidly coupled to the fluid catalytic cracking unit, and a union is coupled to the fluid catalytic cracking compressor and the saturated compressor. A fractionation area is fluidly coupled to the union. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Various embodiments will hereinafter be described in conjunction with the FIGURE, which is a schematic diagram of an oil refining apparatus and methods for producing hydrocarbons using the oil refining apparatus, in accordance with an exemplary embodiment, wherein like numerals denote like elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of the embodiment described. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
         [0010]    In accordance with various exemplary embodiments described herein, an oil refining apparatus includes a crude distillation unit that produces a saturated stream, where the saturated stream is primarily paraffinic compounds. An unsaturated stream may be produced by a cracking device, such as a fluid catalytic cracker or a thermal cracking unit such as a coker. The saturated stream and the unsaturated stream are combined and co-processed to reduce the equipment count necessary in the oil refining apparatus. 
         [0011]    Referring to the exemplary embodiment of an oil refining apparatus  10  illustrated in  FIG. 1 , a crude oil supply  12  is introduced to a crude distillation unit  14 . The crude oil supply  12  includes a mixture of many hydrocarbons, and may include sulfur compounds such as mercaptans and sulfides. The crude oil supply  12  may also include nitrogen compounds. In this description, the hydrocarbons are referred to by the letter “C” followed by a number or range of numbers, where the letter “C” denotes carbon, and the number or range of numbers denotes the number of carbon atoms in a molecule. For example, a C5 hydrocarbon has 5 carbons, and a C5 −  stream includes hydrocarbons with 5 or fewer carbon atoms. The crude oil supply  12  includes C5 −  compounds that are primarily saturated paraffins, with very few if any olefins in the C5 −  range. For example, the C5 −  range of hydrocarbons in the crude oil supply  12  may be about 1 weight percent or less olefins. 
         [0012]    The crude distillation unit  14  fractionates the crude oil supply  12  to produce a plurality of streams differentiated by boiling point, where the “lighter” compounds have a lower boiling point and the “heavier” compounds have a higher boiling point. In an exemplary embodiment, the crude oil supply  12  is fractionated in the crude distillation unit  14  to produce a crude saturated stream  16 , a crude kerosene stream  18 , a crude diesel stream  20 , and a residual stream  22 . The crude distillation unit  14  may produce other hydrocarbons streams in other embodiments, such as a liquid petroleum gas (LPG), jet fuel, and heavy gas oil (not illustrated). The crude distillation unit  14  may include one or more fractionation columns in various embodiments. For example, the crude distillation unit  14  may include a vacuum tower in some embodiments (not illustrated), as further described below. In an exemplary embodiment, the crude distillation unit  14  operates at conditions to provide separation of naphtha and kerosene. In some embodiments, the crude saturated stream  16  primarily includes C10 −  compounds and has an atmospheric boiling range of about −160° C. to about 170° C. The crude kerosene stream  18  may have an atmospheric boiling range of about 170° C. to about 240° C., the crude diesel stream  20  may have an atmospheric boiling range of about 240° C. to about 350° C., and the residual stream  22  may have a boiling range of from about 350° C. and higher. In embodiments with a vacuum tower (not illustrated), the residual stream  22  may have a boiling range of from about 560° C. and higher. Some compounds in the residual stream  22  may decompose before boiling, so the upper limit of the boiling range may not be clearly defined. 
         [0013]    The crude saturated stream  16  is collected from the crude distillation unit  14  in a crude receiver  24 . In this description, process equipment is fluidly coupled together when fluids from one piece of equipment flow to another. The crude saturated stream  16  flows from the crude receiver  24  to a saturated compressor  26 , where the pressure of the crude saturated stream  16  is increased to nominally liquefy material with a boiling point equal to or higher than propane. After the saturated compressor  26 , the crude saturated stream  16  may be fractionated in a naphtha stabilizer  28  to produce a saturated naphtha stream  30  and a saturated stabilizer stream  32 . The naphtha stabilizer  28  is operated at appropriate conditions to separate C5 +  paraffinic hydrocarbons from C4 −  paraffinic hydrocarbons, as understood by those skilled in the art. The saturated naphtha stream  30  primarily includes C5+ compounds as determined by the composition of the crude saturated stream  16 . The saturated stabilizer stream  32  primarily includes C4 −  compounds, and may include hydrogen sulfide or other sulfur compounds as well as nitrogen compounds. 
         [0014]    An unsaturated stream may be formed from a variety of operating units. For example, various cracking devices that “crack” given hydrocarbons into smaller, more volatile hydrocarbons produce olefins. An unsaturated stream typically includes olefins, and various cracking devices or other operating units can be used to produce unsaturated streams. In an exemplary embodiment, the cracking device may be a fluid catalytic cracking unit (FCC unit)  40 , as described below, but other cracking devices may be used in place of, or in addition to, an FCC unit  40  in various embodiments. For example, a coker (not illustrated) is another cracking device that can produce an unsaturated stream, so a coker may be used in place of, or in addition to, an FCC unit  40  to produce an unsaturated stream. An FCC unit  40  is illustrated and described as the cracking device in this description for simplicity and clarity, but other cracking devices or other unsaturated stream sources may be used in place of, or in addition to, an FCC unit  40  in various embodiments. 
         [0015]    Referring back to the crude distillation unit  14 , the residual stream  22  includes high boiling “heavy” compounds. For example, the residual stream  22  may primarily include C20 +  compounds, with about  10  weight percent or less of C19 −  compounds. These high boiling, heavy compounds are introduced to an FCC unit  40  to produce an FCC effluent stream  42 . In the FCC unit  40 , the hydrocarbons in the residual stream  22  are contacted with a cracking catalyst at cracking conditions, and the hydrocarbons are “cracked” or broken down into smaller hydrocarbons with lower boiling points. In an exemplary embodiment, the cracking catalyst includes a high activity crystalline alumina silicate and/or zeolite, which are dispersed in a porous inorganic carrier material such as silica, aluminum, zirconium, or clay. An exemplary embodiment of a catalyst includes crystalline zeolite as the primary active component, a matrix, a binder, and a filler. The zeolite ranges from about 10 to about 50 weight percent of the catalyst, and is a silica and alumina tetrahedral with a lattice structure that limits the size range of hydrocarbon molecules that can enter the lattice. The matrix component includes amorphous alumina, and the binder and filler provide physical strength and integrity. Silica sol or alumina sol are used as the binder and kaolin clay is used as the filler. It will be appreciated, however, that other suitable catalysts can be used in the FCC unit  40 . The cracking conditions may include a temperature of from about 480° C. to about 570° C. and a pressure of from about 100 kilo Pascals gauge (kPa) to about 250 kPa. The FCC unit  40  may produce a wide variety of hydrocarbons, and hydrocarbons from the FCC unit  40  typically include higher concentrations of olefins than in the crude oil supply  12 . 
         [0016]    The FCC effluent stream  42  is introduced into an FCC fractionation unit  44 , where the various hydrocarbons are separated based on boiling point. Several streams may be produced by the FCC fractionation unit  44 , such as an unsaturated stream  46 , an FCC diesel stream  48 , and an FCC heavy cycle oil  50 . The FCC fractionation unit  44  may produce several other streams in various embodiments, as described for the crude distillation unit  14  described above. The FCC fractionation unit  44  may include one or more fractionation columns in various embodiments, and is operated at suitable conditions to separate the various fractions as is understood by those skilled in the art. In an exemplary embodiment, the unsaturated stream  46  primarily includes C10 −  compounds, so the unsaturated stream  46  includes naphtha compounds as well as lighter compounds. The unsaturated stream  46  may include about 10 to about 70 weight percent of olefins in some embodiments, and generally has a higher concentration of olefins than the crude saturated stream  16 . 
         [0017]    In an exemplary embodiment, the unsaturated stream  46  is collected in an FCC receiver  52 , and then pressurized in an FCC compressor  54 . The FCC compressor  54  pressurizes the unsaturated stream  46  to nominally liquefy the C3 +  compounds. The saturated stabilizer stream  32  is combined with the unsaturated stream  46  in a union  61  to produce a combined stream  62  in an exemplary embodiment. The combined stream  62  is introduced to a stripper  56  that produces a stripper C3 +  stream  58  and a stripper C2 −  stream  60 . The stripper C3 +  stream  58  includes C3 +  compounds, and the stripper  56  is operated at conditions that separate C3 +  compounds from CT compounds. The stripper C3 +  stream  58  includes a higher concentration of olefins than the saturated naphtha stream  30 , and may include about 10 to about 70 weight percent olefins. The stripper C2 −  stream  60  includes C2 −  compounds with a higher concentration of olefins than the saturated stabilizer stream  32 , and may include about 10 to about 70 weight percent of olefins. 
         [0018]    The stripper  56  is part of a fractionation area  68 , where the combined stream  62  is fractionated into various components in the fractionation area  68 . The union  61  is coupled to the fractionation area  68 , so the combined stream  62  produced at the union  61  flows to the fractionation area  68 . The fractionation area  68  produces hydrocarbon streams with more narrow boiling ranges than that of the combined stream  62 , where the produced hydrocarbon streams can be used as feedstocks for other processes, as fuels, or in other manners. The fractionation area  68  may include a wide variety of fractionators to separate the combined stream  62  into desired fractions, as understood by those skilled in the art. In an exemplary embodiment, the fractionation area  68  includes the stripper  56 , a debutanizer  74 , and a depropanizer  80 , but the fractionation area  68  may include other fractionators or other arrangements of fractionators in various embodiments. In the illustrated exemplary embodiment, the stripper C3 +  stream  58  flows to the debutanizer  74 . The debutanizer  74  is operated at conditions adequate to separate C4 −  compounds from C5 +  compounds. The debutanizer  74  produces a gasoline stream  76  including C5 +  compounds and a debutanizer effluent  78  primarily including C3 and C4 compounds, such as about 90 weight percent or more C3 and C4 compounds. The gasoline stream  76  may have a boiling range of about 35° C. to about 210° C. The debutanizer effluent  78  flows to the depropanizer  80 , which is operated at conditions that separate C3 compounds from C4 compounds. The depropanizer  80  produces a propyl stream  82  and a butyl stream  84 , where the propyl stream  82  primarily includes C3 compounds (about 90 weight percent or greater C3 compounds including paraffinic and olefinic compounds), and the butyl stream  84  primarily includes C4 compounds (about 90 weight percent or greater C4 compounds including paraffinic and olefinic compounds.) The propyl stream  82 , the butyl stream  84 , and other streams described herein may be further fractionated in some embodiments (not illustrated), such as to separate propene from propane in the propyl stream  82 . 
         [0019]    The stripper C2 −  stream  60  flows to a hydrocarbon absorber system  63  to recover residual C3 and heavier hydrocarbons. An absorber recovery stream  65  flows into the hydrocarbon absorber system  63  and flows past the stripper C2 −  stream  60  in a counter-current flow. The absorber recovery stream  65  exits the hydrocarbon absorber system  63 , and includes C3 and heavier hydrocarbons that may have been entrained in the stripper C2 −  stream  60 . The absorber recovery stream  65  may include naphtha, light cycle oil, or other heavier hydrocarbons that do not vaporize and exit the hydrocarbon absorber system  63  with the stripper C2 −  stream  60 . The absorber recovery stream  65  may be further processed or used after passing through the hydrocarbon absorber system  63 . The hydrocarbon absorber system  63  may include one, two, or more towers in various embodiments. 
         [0020]    In an exemplary embodiment, the stripper C2 −  stream  60  exits the hydrocarbon absorber system  63  and flows to an optional amine absorber  64  to remove hydrogen sulfide and carbon dioxide that may be present in the stripper C2 −  stream  60 . Hydrogen sulfide and carbon dioxide boil at or below the temperature of C3 +  compounds, so hydrogen sulfide and carbon dioxide are separated from the stripper C3 +  stream by the stripper  56 . The amine absorber  64  is coupled to an amine recovery unit  66  to recover the amines for further hydrogen sulfide removal. The amines react with the hydrogen sulfide and carbon dioxide, and produce a rich amine stream  70 . The rich amine stream  70  flows to the amine recovery unit  66 , where the rich amine stream  70  is heated to separate the hydrogen sulfide from the amine solution. The hydrogen sulfide is removed (not illustrated), and the regenerated amine solution is returned to the amine absorber  64  in a lean amine stream  72 . Many amines can be used in the amine absorber  64 , including but not limited to diethanol amine, monoethanol amine, methyldiethanol amine, and diisopropanol amine. The amine absorber  64  produces a refinery fuel gas stream  88  primarily including C2 −  compounds, where the refinery fuel gas stream  88  is largely free of hydrogen sulfide. For example, the refinery fuel gas stream  88  may include about 50 parts per million hydrogen sulfide by volume. 
         [0021]    The fractionation area  68  and the amine absorber  64  process the combined stream  62 , so separate fractionation areas  68  and amine absorbers  64  are not required to separately process the saturated stabilizer stream  32  and the unsaturated stream  46 . However, the relatively olefin rich unsaturated stream  46  is combined with the relatively olefin poor saturated stabilizer stream  32  in the resulting combined stream  62 , so separate fractionated streams with different olefin concentrations are not available. 
         [0022]    The amine absorber  64  and the fractionation area  68  can also be used for other process streams to further reduce process equipment duplication. Many process streams may be hydrotreated to remove sulfur compounds such as mercaptans and sulfides, as well as nitrogen compounds such as amines and oxygenates. The hydrotreating process produces hydrogen sulfide as a by-product, and may produce some smaller, more volatile hydrocarbons from larger, higher boiling compounds. These smaller, more volatile hydrocarbons and other gaseous components, such as hydrogen sulfide, are discharged in a fuel gas stream. The fuel gas stream(s) typically include C1 and C2 compounds, and may contain low concentrations of C3 and C4 compounds, as well as hydrogen sulfide. However, the composition of a fuel gas stream often varies from one source to another. Hydrogen sulfide is volatile, with an atmospheric boiling point of about −60° C., so hydrogen sulfide and other gaseous components are generally discharged from a hydrotreating process in the fuel gas stream. The fuel gas streams from a plurality of hydrotreating units can be added to the combined stream  62  and co-processed. The fuel gas streams can be added to the combined stream  62 , or to the saturated stabilizer stream  32 , the unsaturated stream  46 , or other streams that flow into the combined stream  62  in various embodiments. Many of the fuel gas streams include hydrogen, and the hydrogen may be recovered and re-used (not illustrated) either before or after the fuel gas streams are added to the combined stream  62 . 
         [0023]    In an exemplary embodiment, a hydrocarbon stream is treated in a hydrotreater. Hydrotreating is a well-known process, and involves contacting the hydrocarbon stream and hydrogen gas with a hydrotreating catalyst at hydrotreating conditions. Exemplary hydrotreating conditions in a hydrotreater include a temperature of from about 290° C. to about 400° C. and a pressure of from about 20 to about 140 atmospheres. Oxygen reacts with the hydrogen gas to produce water, sulfur compounds produce hydrogen sulfide, and nitrogen compounds produce ammonia. In an exemplary embodiment, the hydrotreating catalyst includes a Group VI and/or Group VIII active metal component on a support, where the support may be a porous refractory oxide including, but not limited to, alumina, alumina-silica, silica, zeolites, titania, zirconia, boria, magnesia, and combinations thereof. Supports other than refractory oxides are also possible in various embodiments. In some embodiments, other metals are included in the hydrotreating catalyst in addition to or in place of the Group VI and/or Group VIII metals, such as cobalt, nickel, or other metals. For example, metals that may be used in the hydrotreating catalyst include molybdenum, ruthenium, cobalt, nickel, tungsten, and combinations thereof. The calcined metal oxide catalysts may be reacted with sulfur to produce a metal sulfide, such as by contact with a sulfur containing compound including but not limited to hydrogen sulfide, organo sulfur compounds or elemental sulfur. 
         [0024]    There are several optional hydrotreating units illustrated, and additional hydrotreating units may be used. In an exemplary embodiment, the crude kerosene stream  18  enters a crude kerosene hydrotreater  92  and produces a crude kerosene hydrotreater fuel gas stream  94  and a hydrotreated crude kerosene stream  96 . The crude kerosene hydrotreater fuel gas stream  94  and the other hydrotreater fuel gas streams are added to the combined stream  62 , as mentioned above, and the hydrotreated crude kerosene stream  96  may be sold as a product, further processed, or otherwise used. In a similar manner, the crude diesel stream  20  is hydrotreated in a crude diesel hydrotreater  98  to produce a crude diesel hydrotreater fuel gas stream  100  and a hydrotreated crude diesel stream  102 . The saturated naphtha stream  30  is hydrotreated in a saturated naphtha hydrotreater  104  to produce a saturated naphtha hydrotreater fuel gas stream  106  and a hydrotreated saturated naphtha stream  108 . The FCC diesel stream  48  is hydrotreated in an FCC diesel hydrotreater  116  to produce an FCC diesel hydrotreater fuel gas stream  118  and a hydrotreated FCC diesel stream  120 . The crude diesel hydrotreater fuel gas stream  100 , the saturated naphtha hydrotreater fuel gas stream  106 , and the FCC diesel hydrotreater fuel gas stream  118  may be added to the combined stream  62 , either directly or indirectly, such that many fuel gas streams can be co-processed. The hydrotreated crude diesel stream  102 , the hydrotreated saturated naphtha stream  108 , the hydrotreated FCC diesel stream  120 , and other hydrotreated streams may be sold as products, further processed or blended, or otherwise used in various embodiments. Other hydrocarbon streams may be hydrotreated in a similar manner (not illustrated), and the resulting fuel gas stream(s) can be added to the combined stream  62 . 
         [0025]    Other process streams may be included in the combined stream  62  in various embodiments. In one example described above, an unsaturated stream may be produced by a coker (not illustrated) in place of, or in addition to, the FCC unit  40 . The crude distillation unit  14  may include a vacuum tower, and thermal processing of the vacuum tower bottoms (not illustrated) can produce another saturated stream that may be combined with the combined stream  62 . 
         [0026]    A hydrocracking unit  130  is another example of an operation that may produce a saturated stream that is included in the combined stream  62 . In an exemplary embodiment, a hydrocracker feedstock  132  is introduced to the hydrocracking unit  130 . The hydrocracker feedstock  132  may be heavy cycle oil, atmospheric and/or vacuum gas oil, delayed coking gas oil, or other compounds in various embodiments. The hydrocracker feedstock  132  is contacted with a hydrocracking catalyst (not individually illustrated) in the presence of hydrogen at hydrocracking conditions to crack hydrocarbons into smaller hydrocarbons. Exemplary hydrocracking catalysts include zeolitic compounds with a metal from Group VIB and/or VIII, and optionally one or more metals from group VIIA, VIIB, phosphorous, boron, and silicon. Hydrocracking catalysts are known to those skilled in the art. Exemplary reaction conditions include temperatures of about 260° C. to about 430° C., and pressures of about 35 kPa to about 20,000 kPa. Olefinic or aromatic compounds that may be formed in the hydrocracking unit  130  may be hydrogenated to form paraffinic compounds, which can then be separated by fractionation within the hydrocracking unit  130  to produce one or more hydrocracker product streams  134  and a hydrocracker saturated stream  136  including C10 −  compounds. The hydrocracker product stream  134  may be used as a fuel, an intermediate product, further processed or otherwise used. The hydrocracker saturated stream  136  may be added to the combined stream  62  in place of the saturated stabilizer stream  32  from the crude distillation unit  14  in some embodiments, or in addition to the saturated stabilizer stream  32 . In other embodiments, no hydrocracker saturated stream  136  is included in the combined stream  62 . Many refining processes are known to produce various saturated streams or unsaturated streams, and different saturated and unsaturated streams may be combined and then fractionated to reduce the number of fractionation areas  68  required in an oil refining apparatus. 
         [0027]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the application in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing one or more embodiments, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope, as set forth in the appended claims.