Patent Application
20220325189
Systems and methods are provided for upgrading of heavy hydrocarbons.
Oil sands are a type of non-traditional petroleum source that remains challenging to fully exploit. Due to the nature of oil sands, substantial processing can be required at or near the extraction site just to create bitumen/crude oil fractions that are suitable for transport. However, oil sands extraction sites are also often in geographically remote locations, which can substantially increase the construction and maintenance costs for any processing equipment that is used at the oil sands site.
One strategy for preparing bitumen for transport via pipeline is to add a low viscosity diluent to the bitumen. Naphtha fractions are an example of a suitable diluent. However, the diluent can correspond to up to 30 to 50 wt % of the diluted bitumen that is transported. Alternative diluent, such as light crude, could require even greater amounts. This means that a substantial amount of naphtha (and/or other diluent) has to be transported to the extraction site, resulting in substantial cost. The use of such a large volume of diluent also means that the effective capacity of the pipeline is reduced. Additionally, the large volume of diluent consumes capacity in the pipestill or other separator at the destination, thus reducing the available separator capacity at the destination.
An alternative that can reduce the amount of transport diluent is to perform some type of partial upgrading at or near the extraction site. Typically, the goal of partial upgrading is to convert at least a portion of the heavy hydrocarbon feed to produce a partially upgraded crude oil, such as a synthetic crude oil, that is closer to meeting pipeline specifications than the initial feed. Unfortunately, such heavy hydrocarbon feeds also have a tendency to cause fouling or other degradation in processing equipment. As a result, attempting to process such heavy hydrocarbon feeds can require substantial equipment investment in addition to resource investments for reagents and solvents used to process the feeds.
Various types of coking are examples of common methods for processing of heavy hydrocarbon feeds. Coking can be effective for processing of a wide variety of types of heavy hydrocarbon feeds without requiring excessive equipment costs and/or excessive use of additional resources. However, as the boiling range of a feed increases, the hydrogen content of heavy hydrocarbon feed tends to be reduced, leading to increasing amounts of coke production for heavier feeds. Such coke production limits total liquid yields and can further constrain the types of liquid products generated. For example, for feeds including substantial amounts of 566° C.+ components, the coke yields can correspond to 30 wt % or more of the feedstock. When coking is used at remote geographic location, this substantial coke production can pose additional difficulties, as outlets for sale and/or disposal of the coke may be limited.
Coke production also contributes to the difficulties when attempting to hydroprocess feedstocks with substantial contents of 566° C.+ components. Although hydroprocessing typically results in lower coke formation than coking, such coke formation can still lead to rapid fouling and/or degradation of hydroprocessing equipment, including hydroprocessing catalyst. As a result, mitigation of coke formation is a primary concern when attempting to hydroprocess a feed with a substantial content of 566° C.+ components.
Some conventional methods for hydroprocessing of heavy feeds have focused on strategies related to using a solvent and/or recycle stream to reduce the relative amount of 566° C.+ components present in the reaction environment. Conventionally, it is believed that reducing the amount of 566° C.+ components in the reaction environment can reduce or minimize coke formation. Thus, in such strategies, the solvent or recycle stream includes a majority of components that boil below 566° C. This assists with maintaining a lower relative content of 566° C.+ components in the reaction environment. However, this also leads to additional conversion of the recycle stream to lower boiling, lower value products. Additionally, for slurry hydroprocessing reactors, it is conventionally believed that bottoms recycle leads to reduced reactor productivity.
U.S. Pat. No. 5,972,202 describes an example of this strategy for reducing the relative amount of high boiling components in the feed. In U.S. Pat. No. 5,972,202, slurry hydrocracking is performed using a recycle stream corresponding to 65 wt % or less of the fresh feed to the slurry hydrocracking stage. The recycle stream includes a small amount of 524° C.+ material as part of a pitch fraction, while the majority of the recycle stream corresponds to vacuum gas oil boiling range stream described as an aromatic oil. The recycle of the aromatic oil is described as preventing the accumulation of asphaltenes on additive particles in the slurry hydroprocessing environment.
U.S. Pat. No. 6,004,453 describes a similar strategy for performing slurry hydrocracking with a recycle stream comprising a majority of vacuum gas oil boiling range components. It is noted that having a majority of the recycle stream correspond to vacuum gas oil boiling range components is described as being necessary for inclusion of pitch in the recycle stream, in order to prevent coke formation.
U.S. Pat. No. 4,252,634 describes slurry hydroprocessing of a full range bitumen where the volume of the recycle stream is at least twice the volume of the fresh feed delivered to the reactor. The amount of distillate and/or gas oil in the recycle stream is greater than 50 wt %, with the pitch in the recycle stream being defined based on cut point of 524° C. Thus, the portion of 566° C.+ components in the recycle is substantially below 50 wt %. The substantial recycle is described as being useful for preventing coke formation.
U.S. Pat. No. 8,435,400 provides an example of why conventional recycle methods have focused on recycle of lower boiling range portions. In U.S. Pat. No. 8,435,400 slurry hydroprocessing of vacuum resid boiling range feeds is performed in a multi-stage reaction system. Some examples describe performing slurry hydroprocessing with recycle of a bottoms or resid stream from the final stage to an earlier stage, as opposed to having a recycle stream including a majority of lower boiling components. The recycle stream corresponded to roughly 15 wt % of the fresh feed into the reaction system. In the examples, it was reported that operating with recycle required a significantly higher catalyst concentration than once-through operation in order to maintain the same level of feed conversion at a given temperature. Operating with recycle at this increased catalyst concentration appeared to provide no benefit or improvement for the productivity of the reaction system.
U.S. Pat. No. 5,374,348 describes another example of conventional recycle during slurry hydrocracking of feed. A feed including a 524° C.+ portion is processed in a slurry hydrocracking environment in the presence of additive (catalyst) particles. The hydrocracked effluent is fractionated to form a 450° C.+ fraction that also includes a substantial portion of the additive particles. Up to 40 wt % of the 450° C.+ fraction (relative to the weight of fresh feed) is recycled to the slurry hydroconversion reactor. The recycle stream allowed for a reduction in the amount of additive particles required for performing the slurry hydrocracking. Based on the examples, it appears that the reactor productivity after addition of the recycle stream was similar or slightly decreased relative to operating without the recycle stream.
In other types of hydroprocessing environments, use of bottoms recycle would be expected to either reduce reactor productivity or have no impact. U.S. Pat. No. 4,983,273 describes a fixed bed hydrocracking process for use with various feeds. The reaction system includes a hydrotreatment stage and a hydrocracking stage. A series of examples of hydrocracking of a vacuum gas oil boiling range feed are provided. In examples where bottoms recycle is used to return unconverted feed to the hydrotreatment stage, a decrease in reactor productivity for the hydrotreatment stage was observed. In examples where bottoms recycle was used to return unconverted feed to the hydrocracking stage, reactor productivity was substantially not changed, but the yield of distillate boiling range products was increased at the expense of naphtha products and light ends products. An improvement in denitrogenation with recycle to the hydrocracking reactor was also reported.
The other conventional strategy for mitigating coke formation is related to removal of asphaltenes from a recycle stream prior to introducing the recycle stream back into a reactor. Conventionally, it is believed that one of the sources of coke formation is due to loss of ability to maintain asphaltenes in solution in a heavy feedstock. By removing asphaltenes from the processing environment, this incompatibility issue is removed, and therefore coke formation in the reaction environment can be reduced or minimized. While removal of asphaltenes can be effective, the asphaltene content can correspond to 15 wt % or more of the 566° C.+ portion of a feed. Thus, removal of asphaltenes from a recycle stream represents a substantial loss of carbon to low (or possible zero) value products before considering any other losses due to hydroprocessing.
U.S. Pat. No. 9,982,203 provides an example of this type of strategy, where an ebullating bed reactor is used to hydroconvert an atmospheric resid or vacuum resid feed. In some configurations, a recycle stream is returned to the reactor that is formed by deasphalting the hydroconversion bottoms to form deasphalted oil. By definition, a deasphalted oil recycle stream contains a minimized amount of asphaltenes. It is noted that this type of configuration would present additional challenges when attempting to use slurry hydroprocessing, as any catalyst in the hydroconversion bottoms would preferentially be separated into the deasphalter rock, and not the deasphalted oil.
U.S. Pat. No. 4,411,768 describes another example of asphaltene removal. In U.S. Pat. No. 4,411,768, removal of coke precursors is described as enabling higher conversion rates while avoiding reactor fouling. An ebullating bed reactor with a bottoms recycle loop is used for hydroconversion of a heavy feed. Prior to recycle of the hydroconversion bottoms, the bottoms are chilled to a temperature that causes precipitation and/or separation of all toluene insolubles and n-heptane insolubles (i.e., asphaltenes) in the recycle stream. As noted above, this represents a substantial rejection of material, as the n-heptane insolubles can correspond to 15 wt % or more of the 566° C.+ portion of a feed, and the toluene insolubles can correspond to an additional 5 wt % or more of the 566° C.+ portion of a feed.
U.S. Pat. No. 4,808,289 is directed to a method for performing hydroconversion in an ebullating bed unit while avoiding the need to remove coke precursors (such as asphaltenes) from any recycle streams. The solution provided in U.S. Pat. No. 4,808,289 is to perform a limited amount of recycle of flash drum bottoms, where the recycle stream includes at least 50 vol % gas oil boiling range components. In other words, the need to remove asphaltenes is avoided by using the first strategy described above, so that the recycle stream includes 50 vol % or more of lower boiling components.
U.S. Pat. No. 9,868,915 describes systems and methods for processing heavy hydrocarbon feeds using a combination of slurry hydroprocessing and coking. Some of the methods including separating a feed into portions having lower Conradson carbon content and higher Conradson carbon content. The lower Conradson carbon content portion is then processed by coking, while the higher Conradson carbon content portion is processed by slurry hydroprocessing. The slurry hydroprocessing conditions are described as including net conversion of at least 80 wt % relative to either 975° F. (524° C.) or 1050° F. (566° C.). The feed to the slurry hydroprocessing is described as including up to 1.0 wt % of nitrogen.
U.S. Pat. No. 8,568,583 describes a high conversion partial upgrade process for forming a synthetic crude oil from a bitumen feed that includes diluent. After an initial separation to remove the diluent, the partial upgrade process includes hydroprocessing a bottoms fraction of the feed in an ebullating bed reactor. The unconverted bottoms from hydroprocessing are then blended with a portion of the bitumen for inclusion in the final synthetic crude oil.
What is needed are improved systems and methods for preparing bitumen and/or other heavy hydrocarbon crude fractions for pipeline transport. The improved systems and methods would preferably provide one or more of: reduced or minimized dependence on external process streams; reduced or minimized capital equipment costs; reduced or minimized creation of fractions that require an alternate transport method; and reduced or minimized loss of portions of the feed to lower value products, including reducing or minimizing overcracking.
What is further needed are improved compositions that can be derived from bitumen (and/or other heavy hydrocarbon feeds) to facilitate transport of crude oil from an extraction site to a refinery or other destination that can process crude oil. Preferably, such an improved composition can include a reduced or minimized amount of diluent.
U.S. Patent Application Publication 2011/0155639 describes a partial upgrading process. A bitumen feed is separated into various fractions, including two separate portions of atmospheric residue. A first portion of the atmospheric residue is further fractionated to form a vacuum residue. The vacuum residue is hydroconverted in an ebullating bed reactor to form a converted effluent and unconverted bottoms. The unconverted bottoms are combined with the second portion of the atmospheric residue. The blend of unconverted bottoms and atmospheric residue is then combined with the converted effluent, the virgin distillate, and the virgin vacuum gas oil to form a final synthetic crude oil product. The synthetic crude oil product includes a vacuum gas oil content (based on a 975° F. end point) of less than 50 vol %, while also including roughly 17 vol % of unconverted bottoms.
In various aspects, a method for upgrading a heavy hydrocarbon feed is provided. The method includes separating a heavy hydrocarbon feed to form a first fraction comprising 50 wt % or more of a 566° C.+ portion, and one or more additional fractions comprising a 177° C.+ portion. The heavy hydrocarbon feed can include an API gravity of 15° or less. The method further includes exposing at least a portion of the first fraction and a pitch recycle stream to slurry hydroconversion conditions at a combined feed ratio of 1.5 or more to form a hydroconverted effluent. The hydroconversion conditions can include a total conversion of 60 wt % to 89 wt % relative to 524° C. The method further includes separating at least a pitch recycle stream and a second hydroconverted fraction comprising a 177° C.+ portion from the hydroconverted effluent. The pitch recycle stream can include more than 50 wt % of 566° C.+ components. Additionally, the method includes blending at least the one or more additional fractions and at least a portion of the second hydroconverted fraction to form a heavy hydrocarbon product having a kinematic viscosity at 7.5° C. of 500 cSt or less and an API gravity of 18° or more.
All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
In various aspects, an upgraded crude composition is provided, along with systems and methods for making such a composition. The upgraded crude composition can correspond to a “bottomless” crude that has an unexpectedly high percentage of vacuum gas oil boiling range components while having a reduce or minimized amount of components boiling above 593° C. (1100° F.). In some aspects, based in part on the hydroprocessing used to form the upgraded crude composition, the composition can include unexpectedly high contents of nitrogen. Still other unexpected features of the composition can include, but are not limited to, an unexpectedly high nitrogen content in the naphtha fraction; and an unexpected vacuum gas oil fraction including an unexpectedly high content of polynuclear aromatics, an unexpectedly high content of waxy, paraffinic compounds, and/or an unexpectedly high content of n-pentane asphaltenes.
The general method for forming the upgraded crude composition can include performing hydroconversion on a vacuum resid portion of the initial bitumen feed (and/or other heavy hydrocarbon feed) to form one or more hydroconverted fractions in the naphtha, distillate, and/or vacuum gas oil boiling range. The one or more hydroconverted fraction can be combined with distillate and/or vacuum gas oil fractions from the feed to form the upgraded crude composition. During the hydroconversion, a vacuum resid portion of the feed is passed into a hydroconversion reactor, such as a slurry hydroconversion reactor, for hydroprocessing under relatively mild per-pass conversion conditions. Any light ends generated during hydroprocessing can be removed and optionally further processed, if desired. The effluent from hydroprocessing can be separated to form at least a bottoms fraction and one or more additional hydroconverted product fractions. A substantial portion of the bottoms fraction can correspond to 566° C.+ components. Most of the bottoms fraction can be recycled for use as part of the input to the hydroconversion reactor, while a smaller, remaining portion of the bottoms fraction is withdrawn as a pitch product. Using the above general method, a hydroconversion reactor operated under relatively mild per-pass conversion conditions can be used to convert up to 89 wt % of the feed (relative to 524° C.) to form the one or more hydroconverted fractions.
In some aspects, a hydroconverted fraction for inclusion in the upgraded crude composition is also provided. The hydroconverted fraction can correspond to a fraction produced by hydroconversion of a vacuum resid portion of the bitumen. By processing the vacuum resid portion under relatively low per-pass conversion conditions with recycle, the yield of vacuum gas oil in the hydroconverted fraction can be enhanced relative to naphtha and/or distillate yield. Additionally, due in part to the low per-pass conversion conditions, the nitrogen content of the various boiling range portions in the hydroconverted fraction can be unexpectedly high.
In some aspects, the yield of the upgraded crude composition relative to the initial feed can be between 90 vol % and 100 vol %. It is noted that the composition includes vacuum gas oil that is formed by conversion of vacuum resid under hydroprocessing conditions. As a result, some volume swell occurs relative to the initial feed volume. However, the unconverted bottoms from hydroprocessing are not included in the composition. As a result, even though some volume swell occurs, in some aspects the net volume yield of the composition can be lower than the volume of the initial heavy hydrocarbon feed.
In some aspects, the compositions described herein can be formed by processing of a bitumen derived from Canadian oil sands, such as western Canadian oil sands. In such aspects, one or more unusual features of bitumen derived from Canadian oil sands can have a synergistic interaction with the methods described herein to result in further unexpected compositional features. For example, the paraffin content of western Canadian oil sands can be relatively low in comparison with other crude sources. As a result, the Solubility Blending Number of vacuum gas oil generated by conversion of the 566° C.+ portion of the bitumen can be relatively high. This can allow for formation of a partially upgraded heavy hydrocarbon product with an unexpectedly high content of vacuum gas oil while having little or no content of vacuum resid (566° C.+) components. As another example, due in part to the reduced paraffin content, the viscosity of vacuum gas oil generated from conversion of the 566° C.+ portion of the bitumen can be higher than vacuum gas oil derived from other crude sources. For example, the kinematic viscosity at 40° C. for vacuum gas oil formed by conversion of bitumen from western Canadian oil sands can be roughly 100 cSt to 150 cSt, as opposed to less than 60 cSt for vacuum gas oil from various typical sources.
In this discussion, unless otherwise specified, “conversion” of a feedstock or other input stream is defined as conversion relative to a conversion temperature of 524° C. (975° F.). Per-pass conversion refers to the amount of conversion that occurs during a single pass through a reactor/stage/reaction system. It is noted that recirculation streams (i.e., streams having substantially the same composition as the liquid in the reactor) are considered as part of the reactor, and therefore are included in the calculation of per-pass conversion. Net or overall conversion refers to the net products from the reactor/stage/reaction system, so that any recycle streams are included in the calculation of the net or overall conversion. It is noted that in all aspects described herein, the amount of conversion at 524° C. is lower than the corresponding conversion at 566° C.
In this discussion, the productivity of a reactor/reaction system is defined based on the feed rate of fresh feed to the reactor/reaction system that is required in order to maintain a target level of net conversion relative to 524° C. at constant temperature. An increase in fresh feed rate while maintaining net conversion at constant temperature corresponds to an increase in productivity for a reactor/reaction system.
In this discussion, primary cracking is defined as cracking of 566° C.+ components in the feed. Secondary cracking refers to any cracking of 566° C.− components.
In this discussion, gas holdup refers to the amount of gas present within the reactor at a given moment in time.
In this discussion, the “combined feed ratio” (or CFR) is defined as a ratio corresponding to (mass flow rate of fresh feed+mass flow rate of recycle stream)/(mass flow rate of fresh feed). Based on this definition, the combined feed ratio when no recycle is used is 1.0. When recycle is present, the relative mass flow rate of the recycle stream as a percentage of the fresh feed can be added to 1.0 to provide the combined feed ratio. Thus, when the mass flow rate of the recycle stream is 10% of the mass flow rate of the fresh feed, the CFR is 1.1. When the mass flow rate of the recycle stream is 50% of the mass flow rate of the fresh feed, the CFR is 1.5. When the mass flow rate of the recycle stream is 100% of the mass flow rate of the fresh feed, the CFR is 2.0.
In this discussion, when describing the amount of a fresh feed stream, recirculation stream, recycle stream, or other stream, the mass flow rate of the stream may also be referred to as a “weight” of the stream.
In this discussion, the Liquid Hourly Space Velocity (LHSV) for a feed or a portion of a feed to a slurry hydrocracking reactor is defined as the volume of feed per hour relative to the volume of the reactor.
In this discussion, a “Cx” hydrocarbon refers to a hydrocarbon compound that includes “x” number of carbons in the compound. A stream containing “Cx-Cy” hydrocarbons refers to a stream composed of one or more hydrocarbon compounds that includes at least “x” carbons and no more than “y” carbons in the compound. It is noted that a stream comprising Cx-Cy hydrocarbons may also include other types of hydrocarbons, unless otherwise specified.
In this discussion, “Tx” refers to the temperature at which a weight fraction “x” of a sample can be boiled or distilled. For example, if 40 wt % of a sample has a boiling point of 343° C. or less, the sample can be described as having a T40 distillation point of 343° C. In this discussion, boiling points can be determined by a convenient method based on the boiling range of the sample. This can correspond to ASTM D2887, or for heavier samples ASTM D7169.
In this discussion, references to “fresh feed” to a hydroconversion stage correspond to feedstock that has not been previously passed through the hydroconversion stage. This is in contrast to recycled feed portions that are formed by fractionation and/or other separation of the products from the hydroconversion stage.
In this discussion, two types of diluents are referred to. One type of diluent is an optional extraction site diluent that can be used for transport of a heavy hydrocarbon feed from an extraction site to the hydroconversion site. For example, when the heavy hydrocarbon feed corresponds to a bitumen, an initial froth treatment for forming a bitumen may be performed at the extraction site, while the hydroconversion site may be some distance away. Although a dedicated pipeline may be available for this transport of the heavy hydrocarbon feed from the extraction site to the hydroconversion site, some type of transport standards may need to be achieved. The extraction site diluent used for transport from the extraction site to the hydroconversion site can be removed at the hydroconversion site by any convenient method, such as by distillation. It is noted that if the hydroconversion reaction train is in sufficient proximity to the extraction site, an extraction site diluent may not be required. A second type of diluent is a transport diluent. A transport diluent is a diluent that is incorporated into a processed heavy hydrocarbon product to allow the product to meet transport specifications (such as pipeline specifications). Typical diluents for use as either an extraction site diluent or a transport diluent can include various types of naphtha boiling range fractions. It is noted that naphtha boiling range components formed during hydroconversion are not considered transport diluent under this definition, as naphtha compounds formed during slurry hydroconversion are derived in-situ from the feed rather than being added to the processed heavy hydrocarbon product.
In this discussion, reference is made to “heavy hydrocarbon feed” or “heavy hydrocarbon feedstock, and “initial feed” or “initial feedstock”. The heavy hydrocarbon feed corresponds to a heavy hydrocarbon feed as described in the “Feedstocks—General” section below. In order to transport a heavy hydrocarbon feed from an extraction site to the location of the hydroconversion system, an extraction site diluent may be added to the heavy hydrocarbon feed. In some aspects, the extraction site diluent can correspond to a naphtha fraction. In such aspects, the heavy hydrocarbon feed plus the extraction site diluent used to transport the heavy hydrocarbon feed to the hydroconversion system can be referred to as an “initial feed” or “initial feedstock”. A separation can be performed to remove some or all of the extraction site diluent prior to further processing of the heavy hydrocarbon fee and/or prior to incorporation of the heavy hydrocarbon feed into the partially upgraded heavy hydrocarbon product. Such a separation performed on an “initial feedstock” can be used to recover a fraction corresponding to extraction site diluent, and a fraction corresponding to the heavy hydrocarbon feed that optionally still contains a remaining portion of the extraction site diluent. In other aspects, the extraction site diluent can include distillate and/or vacuum gas oil boiling range components. Such distillate and/or vacuum gas oil boiling range components of an extraction site diluent can be processed in the same manner as other distillate and/or vacuum gas oil boiling range components It is noted that unless otherwise specified (such as based on boiling range) references to “heavy hydrocarbon feed” do not exclude the possible presence of extraction site diluent.
In various aspects of the invention, reference may be made to one or more types of fractions generated during distillation of a petroleum feedstock, intermediate product, and/or product. Such fractions may include naphtha fractions, distillate fuel fractions, and vacuum gas oil fractions. Each of these types of fractions can be defined based on a boiling range, such as a boiling range that includes at least 90 wt % of the fraction, or at least 95 wt % of the fraction. For example, for naphtha fractions, at least 90 wt % of the fraction, or at least 95 wt %, can have a boiling point in the range of 85° F. (29° C.) to 350° F. (177° C.). It is noted that 29° C. roughly corresponds to the boiling point of isopentane, a C5 hydrocarbon. For a distillate fuel fraction, at least 90 wt % of the fraction, or at least 95 wt %, can have a boiling point in the range of 350° F. (177° C.) to 650° F. (343° C.). For a vacuum gas oil fraction, at least 90 wt % of the fraction, or at least 95 wt %, can have a boiling point in the range of 650° F. (343° C.) to 1050° F. (566° C.). Fractions boiling below the naphtha range can sometimes be referred to as light ends. Fractions boiling above the vacuum gas oil range can be referred to as vacuum resid fractions or pitch fractions.
Another option for specifying various types of boiling ranges can be based on a combination of T5 (or T10) and T95 (or T90) distillation points. For example, in some aspects, having at least 90 wt % of a fraction boil in the naphtha boiling range can correspond to having a T5 distillation point of 29° C. or more and a T95 distillation point of 177° C. or less. In some aspects, having at least 90 wt % of a fraction boil in the distillate boiling range can correspond to having a T5 distillation point of 177° C. or more and a T95 distillation point of 343° C. or less. In some aspects, having at least 90 wt % of a fraction boil in the vacuum gas oil range can correspond to having a T5 distillation point of 343° C. or more and a T95 distillation point of 566° C. or less.
In this discussion, the boiling range of components in a feed, intermediate product, and/or final product may alternatively be described based on describing a weight percentage of components that boil within a defined range. The defined range can correspond to a range with an upper bound, such as components that boil at less than 177° C. (referred to as 177° C.−); a range with a lower bound, such as components that boil at greater than 566° C. (referred to as 566° C.+); or a range with both an upper bound and a lower bound, such as 343° C.-566° C.
In various aspects, formation of an upgraded crude composition is facilitated by first forming one or more hydroconverted fractions from a vacuum resid portion of a feed. For convenience, the one or more hydroconverted fractions are described herein as a hydroconverted naphtha fraction (i.e., a naphtha boiling range fraction), a hydroconverted distillate fraction (i.e., distillate boiling range fraction), and a hydroconverted vacuum gas oil fraction (i.e., vacuum gas oil boiling range fraction). It is understood, however, that this description is for convenience in explanation only, and any other suitable fractionation of the hydroconverted effluent could be performed, including not performing a separation. These hydroconverted fractions can have one or more of the following unexpected compositional characteristics, which in turn contribute to the unexpected nature of the upgraded crude composition.
Relative to the total product from hydroconversion, the hydroconverted naphtha fraction can correspond to 14 wt % to 30 wt % of the total hydroconversion product, or 14 wt % to 25 wt %, or 18 wt % to 30 wt %, or 21 wt % to 30 wt %; the hydroconverted distillate can correspond to 14 wt % to 30 wt % of the total hydroconversion product, or 14 wt % to 25 wt %, or 18 wt % to 30 wt %, or 21 wt % to 30 wt %; and the hydroconverted vacuum gas oil can correspond to 30 wt % to 60 wt % of the total hydroconversion product, or 30 wt % to 50 wt %, or 35 wt % to 55 wt %, or 35 wt % to 60 wt %, or 40 wt % to 60 wt %. The fractions correspond to the one or more fractions that are added to the upgraded crude composition. In addition to the above fractions, the hydroconversion stage can also produce roughly 5.0 wt % to 8.0 wt % of light ends and 6.0 wt % to 20 wt % (or 10 wt % to 20 wt %) of pitch or unconverted bottoms. Without being bound by any particular theory, it is believed that the unexpectedly high content of vacuum gas oil in the hydroconversion effluent, relative to the hydroconverted naphtha and/or hydroconverted distillate, is due in part to the relatively mild per-pass conversion conditions used to form the hydroconverted fractions.
In some aspects, the hydroconverted fractions can have an unexpectedly high content of nitrogen. Without being bound by any particular theory, it is believed that the relatively high nitrogen contents are due in part to achieving a high total conversion amount based on relatively low per-pass conversion with substantial recycle. Under these conditions, it is believed that conversion of compounds relative to 1050° F. (566° C.) or 1100° F. (593° C.) is favored while performing only limited amounts of hydrodenitrogenation (and/or hydrodesulfurization).
In some aspects, the hydroconverted naphtha fraction can have a nitrogen content of 0.06 wt % to 0.4 wt %, or 0.10 wt % to 0.3 wt %, or 0.15 wt % to 0.4 wt %. This is an unexpectedly high nitrogen content for a naphtha fraction produced by a conversion process. For example, a typical coker naphtha would be expected to have a nitrogen content of 0.01 wt % to 0.05 wt % (100 wppm to 500 wppm). A hydrocracked naptha formed by conventional methods would typically be expected to have a still lower nitrogen content. It is further noted that the sulfur content of the hydroconverted naphtha can be similar to the sulfur content of a coker naphtha. For example, the hydroconverted naphtha fraction can have a sulfur content of 0.2 wt % to 1.5 wt %, which is comparable to a typical coker naphtha sulfur content of 0.5 wt % to 1.0 wt %. Additionally or alternatively, the hydroconverted distillate fraction can have a nitrogen content of 0.2 wt % to 1.2 wt %, or 0.4 wt % to 1.2 wt %, or 0.4 wt % to 1.0 wt %, or 0.6 wt % to 1.2 wt %, or 0.6 wt % to 1.0 wt %. The hydroconverted vacuum gas oil fraction can have a nitrogen content of 0.6 wt % to 2.0 wt %, or 0.6 wt % to 1.6 wt %, or 1.0 wt % to 2.0 wt %, or 0.8 wt % to 1.6 wt %, or 0.8 wt % to 2.0 wt %.
Because the nitrogen contents of the hydroconverted fractions are somewhat dependent on the nitrogen content of the initial input flow to hydroconversion, another way of characterizing the elevated nitrogen contents of the hydroconverted fractions is based on the nitrogen content relative to the initial input flow to hydroconversion. For the hydroconverted naphtha fraction, the weight of nitrogen in the hydroconverted naphtha fraction can be 15% to 30% (or 15% to 25%) of the weight of nitrogen in the input flow to hydroconversion. For the hydroconverted distillate fraction, the weight of nitrogen in the hydroconverted naphtha fraction can be 50% to 80%, or 50% to 70%, or 60% to 80%, of the weight of nitrogen in the input flow to hydroconversion. For the hydroconverted vacuum gas oil fraction, the weight of nitrogen in the hydroconverted naphtha fraction can be 70% to 120%, or 70% to 110%, or 80% to 110%, or 100% to 120% of the weight of nitrogen in the input flow to hydroconversion. It is noted that in some aspects, the nitrogen content in the hydroconverted vacuum gas oil fraction can be greater than the nitrogen content of the input flow to hydroconversion. Without being bound by any particular theory, this is believed to be due to use of hydroconversion conditions with low per-pass conversion while only recycling unconverted portions of the effluent. This is believed to lead to boiling point conversion of resid components to vacuum gas oil components while resulting in a reduced or minimized amount of heteroatom removal.
Another unexpected feature can be an unexpectedly high kinematic viscosity for the hydroconverted vacuum gas oil fraction. In some aspects, the kinematic viscosity at 40° C. of the hydroconverted vacuum gas oil fraction can be 100 cSt or more, or 150 cSt or more. This unexpectedly high kinematic viscosity can be due in part to the formation of this fraction by conversion of vacuum resid to vacuum gas oil under conditions with relatively low per-pass conversion. Additionally or alternately, the kinematic viscosity of a 510° C.+ portion of vacuum gas oil, or a 524° C.+ portion of vacuum gas oil, can be still greater. For example, the kinematic viscosity at 40° C. for a 510° C.+ portion of vacuum gas oil (or a 524° C.+ portion) can be 150 cSt to 250 cSt.
Depending on the aspect, still another unexpected feature can be an unexpectedly high concentration of naphthenes and aromatics in the hydroconverted fractions. For the hydroconverted naphtha fraction, this can correspond to having a combined naphthenes and aromatics content of 15 wt % to 30 wt % (or 20 wt % to 30 wt %), as opposed to 5 wt % to 10 wt % for a conventional virgin naphtha fraction. For the hydroconverted distillate fraction, this can correspond to a combined naphthenes and aromatics content of 40 wt % to 60 wt %, as opposed to 20 wt % to 30 wt % for a conventional virgin distillate fraction. For the hydroconverted vacuum gas oil fraction, this can correspond to a combined naphthenes and aromatics content of 70 wt % to 90 wt %, as opposed to 30 wt % to 40 wt % for a conventional virgin vacuum gas oil fraction.
In various aspects, a stabilization stage can be included after a hydroconversion stage to allow for olefin saturation of one or more of the hydroconverted fractions. Depending on the aspect, at least a portion of the hydroconverted naphtha fraction can be exposed to the stabilizer conditions, or the hydroconverted distillate fraction, or the hydroconverted vacuum gas oil fraction, or at least a portion of two or more of the above, or at least a portion of all of the above. Prior to stabilization, the hydroconverted naphtha fraction can have an olefin content of 2.0 wt % to 15 wt %, or 2.0 wt % to 10 wt %. Additionally or alternately, prior to stabilization, the hydroconverted distillate fraction can have an olefin content of 2.0 wt % to 10 wt %, or 2.0 wt % to 6.0 wt %. After stabilization, the olefin content can be reduced in the stabilized hydroconverted naphtha fraction to 0.1 wt % to 1.5 wt %. After stabilization, the olefin content can be reduced in the stabilized hydroconverted distillate fraction to 0.1 wt % to 1.5 wt %.
Upgraded Synthetic Crude Composition
In various aspects, the heavy hydrocarbon product can correspond to an upgraded synthetic crude composition. An upgraded synthetic crude composition can include a variety of unexpected features. In such aspects, the unexpected features can include, but are not limited to, a reduced or minimized content of vacuum resid or “bottoms”; an unexpectedly high content of vacuum gas oil; an unexpectedly high nitrogen content and/or kinematic viscosity in one or more fractions of the composition, such as in a portion formed from hydroconversion of the feed bottoms; unexpected relative contents of naphthenes, aromatics, and/or paraffins in one or more fractions of the composition; and/or unexpectedly high content of metals and/or micro carbon residue.
In some aspects, the upgraded synthetic crude composition can generally correspond to a “bottomless” crude composition. In other words, vacuum tower bottoms are not added to the upgraded synthetic crude composition. Thus, the upgraded synthetic crude composition can contain a reduced or minimized amount of components with a boiling point of 676° C. (1250° F.) or more, or 593° C. (1100° F.) or more. Depending on the aspect, the amount of 593° C.+ components in the upgraded synthetic crude composition can be 5.0 wt % or less relative to a weight of the upgraded crude composition, or 3.0 wt % or less, or 1.0 wt % or less, such as down to having substantially no 593° C.+ components (less than 0.1 wt %). In some aspects, in addition to having a reduced or minimized amount of 593° C.+ components, the upgraded crude composition can contain substantially no 676° C.+ components (0.1 wt % or less), or substantially no 649° C.+ components (0.1 wt % or less), or substantially no 621° C.+ components (0.1 wt % or less).
With regard to fractions within the upgraded synthetic crude composition, the fractions can be distinguished based on both boiling range and based on whether a fraction is separated directly from the bitumen (a virgin fraction) or formed from conversion of vacuum resid (a hydroconverted fraction). The upgraded crude composition can include 6.0 wt % to 12 wt % hydroconverted naphtha, 6.0 wt % to 12 wt % hydroconverted distillate, 15 wt % to 25 wt % hydroconverted vacuum gas oil, 6.0 wt % to 14 wt % virgin distillate, and 36 wt % to 60 wt % virgin vacuum gas oil. After blending of the various fractions, this can produce a upgraded synthetic crude composition including 6.0 wt % to 12 wt % of a naphtha fraction, 10 wt % to 35 wt % (or 15 wt % to 30 wt %, or 15 wt % to 35 wt %, or 20 wt % to 35 wt %) of a distillate fraction, and 50 wt % or more (or 60 wt % or more) of a vacuum gas oil fraction. In some aspects, the upgraded crude composition can have 6.0 wt % to 20 wt % of a naphtha fraction, or 6.0 wt % to 15 wt %. In such aspects, the additional naphtha corresponds to transport diluent added to the upgraded crude composition to facilitate transport.
In some aspects, a partially processed heavy hydrocarbon product can be formed where an upgraded synthetic crude composition is blended with a bypass portion of the heavy hydrocarbon feed. This can create a partially processed heavy hydrocarbon product that corresponds to a sour heavy crude. In aspects where the blended product (i.e., the partially processed heavy hydrocarbon product) includes a bypass portion of the heavy hydrocarbon feed, the composition can include 3.0 wt % to 15 wt % of a naphtha fraction, 10 wt % to 35 wt % (or 15 wt % to 30 wt %, or 15 wt % to 35 wt %, or 20 wt % to 35 wt %) of a distillate fraction, 15 wt % to 30 wt % of 566° C.+ components, and 40 wt % to 65 wt % of a vacuum gas oil fraction.
It is noted that in aspects where a heavy hydrocarbon feed is being used to form the upgraded crude composition, it can be beneficial to form the upgraded crude composition while limiting the number of external feed sources that are required. In such aspects, the hydrocracked distillate fraction can be derived from the same source as the virgin distillate fraction, and/or the hydrocracked vacuum gas oil fraction can be derived from the same source as the virgin vacuum gas oil fraction. As an example of deriving fractions from the same source: A bitumen feedstock can be a suitable heavy hydrocarbon feed. The bitumen can be initially separated to form virgin distillate, virgin vacuum gas oil, and vacuum resid. The vacuum resid can then be hydroconverted to form hydrocracked distillate and hydrocracked vacuum gas oil. In this example, the hydroconverted distillate is derived from the same source (i.e., the bitumen feedstock) as the virgin distillate. Similarly, the hydroconverted vacuum gas oil is derived from the same source as the virgin vacuum gas oil.
Due in part to unexpectedly high nitrogen contents in the hydroconverted fractions, the nitrogen content of the upgraded crude composition can also be unexpectedly high. In some aspects, the nitrogen content of the upgraded synthetic crude composition can be 0.2 wt % to 1.5 wt %, or 0.3 wt % to 1.5 wt %. With regard to the fractions within the upgraded synthetic crude composition, the naphtha fraction can have a nitrogen content of 0.06 wt % to 0.4 wt %, or 0.1 wt % to 0.4 wt %, or 0.06 wt % to 0.3 wt %, or 0.1 wt % to 0.3 wt %. The distillate fraction can include 0.1 wt % to 0.6 wt % of nitrogen, or 0.2 wt % to 0.6 wt %. The vacuum gas oil fraction can include 0.3 wt % to 1.5 wt % nitrogen, or 0.4 wt % to 1.5 wt %, or 0.6 wt % to 1.5 wt %, or 0.3 wt % to 1.0 wt %.
In aspects where a bypass portion of the heavy hydrocarbon feed is added to the partially upgraded heavy hydrocarbon product, the nitrogen content of the partially upgraded heavy hydrocarbon product can be 0.1 wt % to 2.0 wt %, or 0.2 wt % to 2.0 wt %, or 0.1 wt % to 1.5 wt %, or 0.2 wt % to 1.5 wt %. With regard to the fractions within the upgraded synthetic crude composition, the naphtha fraction can have a nitrogen content of 0.06 wt % to 0.4 wt %, or 0.1 wt % to 0.4 wt %, or 0.06 wt % to 0.3 wt %, or 0.1 wt % to 0.3 wt %. The distillate fraction can include 0.06 wt % to 0.6 wt % of nitrogen, or 0.1 wt % to 0.6 wt %. The vacuum gas oil fraction can include 0.15 wt % to 1.2 wt % nitrogen, or 0.2 wt % to 1.2 wt %, or 0.3 wt % to 1.2 wt %, or 0.15 wt % to 1.0 wt %.
In other aspects, the hydroconverted naphtha fraction and/or the hydroconverted distillate fraction can be hydrotreated to reduce or minimize the nitrogen content. In such aspects, the nitrogen content of the hydroconverted naphtha fraction and/or the hydroconverted distillate fraction can be substantially reduced. In such aspects, the nitrogen content of the hydroconverted naphtha fraction can be 10 wppm to 1000 wppm, or 50 wppm to 1000 wppm or 10 wppm to 500 wppm, or 50 wppm to 500 wppm. In such aspects, the nitrogen content of the hydroconverted naphtha fraction can be 10 wppm to 1500 wppm, or 100 wppm to 1500 wppm or 10 wppm to 1000 wppm, or 100 wppm to 1000 wppm.
The combined content of naphthenes and aromatics in the upgraded synthetic crude composition can also be unexpectedly high. In some aspects, the combined naphthenes and aromatics content in the distillate portion of the upgraded synthetic crude composition can be 30 wt % to 50 wt %, or 32 wt % to 50 wt %. In some aspects, the combined naphthenes and aromatics content in the vacuum gas oil portion of the upgraded synthetic crude composition can be 60 wt % to 80 wt %. In some aspects, the combined naphthenes and aromatics content in the naphtha portion of the upgraded crude composition can be 10 wt % to 30 wt %, or 15 wt % to 30 wt %. The lower end of the naphthenes and aromatics content for the naphtha fraction can correspond to aspects where an additional naphtha fraction is added as a transport diluent. In aspects where a bypass portion of the heavy hydrocarbon feed is added to the partially upgraded heavy hydrocarbon product, the combined naphthenes and aromatics in the distillate portion of the partially upgraded heavy hydrocarbon product can be 20 wt % to 50 wt %, or 25 wt % to 50 wt %, or 30 wt % to 50 wt %. The combined naphthenes and aromatics in the vacuum gas oil portion of the partially upgraded heavy hydrocarbon product can be 40 wt % to 70 wt %, or 50 wt % to 70 wt %.
In addition to characterizing naphthenes and aromatics, the paraffin content of the vacuum gas oil fraction can also be characterized. In aspects where the virgin vacuum gas oil fraction corresponds to vacuum gas oil from a western Canadian bitumen, the paraffin content of the virgin vacuum gas oil can be 3.0 wt % or less, or 1.0 wt % or less, such as down to 0.01 wt % or possibly still lower. Due to a marginally higher paraffin content in the hydrocracked vacuum gas oil fraction, the total vacuum gas oil fraction in an upgraded crude composition can have a paraffin content of 5.0 wt % or less, or 3.0 wt % or less, or 1.0 wt % or less, such as down to 0.01 wt % or possibly still lower.
The relatively low paraffin content in the hydroconverted vacuum gas oil fraction and the virgin vacuum gas oil fraction can result in a total vacuum gas oil fraction with a relatively high solubility blending number (SBN). Solubility blending number is described in U.S. Pat. No. 5,187,634, which is incorporated herein by reference for the limited purpose of describing (IN), (SBN), and methods for determining IN and SBN. The solubility number for the virgin vacuum gas oil fraction and/or for the vacuum gas oil in the upgraded crude composition can be 60 or more, or 70 or more, such as up to 100 or possibly still higher.
The vacuum gas oil portion of the upgraded synthetic crude composition can also have an unexpectedly high content of Ni, V, and Fe and/or an unexpectedly high content of micro carbon residue. Based on processing under hydroconversion conditions, the hydroconverted vacuum gas oil can have a combined content of Ni, V, and Fe that is below 1 wppm. However, the virgin vacuum gas oil fraction in the upgraded crude composition can have a combined content of Ni, V, and Fe of 2.0 wppm to 20 wppm. The content of micro carbon residue content of the hydroconverted vacuum gas oil fraction can be 1.0 wt % to 10 wt %. For the total vacuum gas oil fraction, the micro carbon residue content can be 1.0 wt % to 8.0 wt %, or 0.5 wt % to 8.0 wt %, or 0.5 wt % to 5.0 wt %. Additionally or alternately, after vacuum distillation to remove pitch, the 343° C.+ portion of the hydroconverted effluent can have a micro carbon residue of 1.0 wt % to 10 wt %, or 3.0 wt % to 10 wt %, or 1.0 wt % to 8.0 wt %, or 5.0 wt % to 10 wt %.
In addition to the above properties, in various aspects, the upgraded crude composition can correspond to a composition that is suitable for pipeline transport. To be suitable for pipeline transport, the upgraded crude composition can have one or more of a kinematic viscosity at 7.5° C. of 360 cSt or less, or 350 cSt or less; an API gravity of 19° or more; and an olefin content of 1.0 wt % or less. It is noted that other blending may occur after forming the upgraded crude composition. Thus, in some aspects, the upgraded crude composition can have properties that are sufficiently close to the standard for pipeline transport. In such aspects, the upgraded crude composition can have one or more of a kinematic viscosity at 7.5° C. of 500 cSt or less, or 400 cSt or less, and an API gravity of 18° or more.
In various aspects, a heavy hydrocarbon feed can be processed to form a partially upgraded heavy hydrocarbon product. Examples of heavy hydrocarbon feeds include, but are not limited to, heavy crude oils, oils (such as bitumen) from oil sands, and heavy oils derived from coal, and blends of such feeds. In some aspects, heavy hydrocarbon feeds can also include at least a portion corresponding to a heavy refinery fraction, such as distillation residues, heavy oils coming from catalytic treatment (such as heavy cycle slurry oils or main column bottoms from fluid catalytic cracking), and/or thermal tars (such as oils from visbreaking, steam cracking, or similar thermal or non-catalytic processes). Heavy hydrocarbon feeds can be liquid or semi-solid. Such heavy hydrocarbon feeds can include a substantial portion of the feed that boils at 650° F. (343° C.) or higher. For example, the portion of a heavy hydrocarbon feed that boils at less than 650° F. (343° C.) can correspond to 5 wt % to 40 wt % of the feed, or 10 wt % to 30 wt % of the feed, or 5 wt % to 20 wt % of the feed. In such aspects, the heavy hydrocarbon feed can have a T40 distillation point of 343° C. or higher, or a T30 distillation point of 343° C. or higher, or a T20 distillation point of 343° C. or higher. Additionally or alternately, a substantial portion of a heavy hydrocarbon feed can also correspond to compounds with a boiling point of 566° C. or higher. In some aspects, 50 wt % or more of a heavy hydrocarbon feed can have a boiling point of 566° C. or more, or 60 wt % or more, or 70 wt % or more, or 80 wt % or more, such as up to substantially all of the heavy hydrocarbon feed corresponding to components with a boiling point of 566° C. or more. In some aspects, 50 wt % or more of a heavy hydrocarbon feed can have a boiling point of 593° C. or more, or 60 wt % or more, or 70 wt % or more, or 80 wt % or more, such as up to substantially all of the heavy hydrocarbon feed corresponding to components with a boiling point of 593° C. or more. In this discussion, boiling points can be determined by a convenient method, such as ASTM D2887, ASTM D7169, or another suitable standard method.
Density, or weight per volume, of the heavy hydrocarbon can be determined according to ASTM D287-92 (2006) Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method), and is provided in terms of API gravity. In general, the higher the API gravity, the less dense the oil. API gravity can be 16° or less, or 12° or less, or 8° or less.
Heavy hydrocarbon feeds can be high in metals. For example, the heavy hydrocarbon feed can be high in total nickel, vanadium and iron contents. In one embodiment, the heavy oil will contain at least 0.00005 grams of Ni/V/Fe (50 ppm) or at least 0.0002 grams of Ni/V/Fe (200 ppm) per gram of heavy oil, on a total elemental basis of nickel, vanadium and iron. In other aspects, the heavy oil can contain at least about 500 wppm of nickel, vanadium, and iron, such as at least about 1000 wppm.
Heteroatoms such as nitrogen and sulfur are typically found in heavy hydrocarbon feeds, often in organically-bound form. Nitrogen content can range from about 0.1 wt % to about 3.0 wt % elemental nitrogen, or 1.0 wt % to 3.0 wt %, or 0.1 wt % to 1.0 wt %, based on total weight of the heavy hydrocarbon feed. The nitrogen containing compounds can be present as basic or non-basic nitrogen species. Examples of basic nitrogen species include quinolines and substituted quinolines. Examples of non-basic nitrogen species include carbazoles and substituted carbazoles.
The invention is particularly suited to treating heavy oil feedstocks containing at least 0.1 wt % sulfur, based on total weight of the heavy hydrocarbon feed. Generally, the sulfur content can range from 0.1 wt % to 10 wt % elemental sulfur, or 1.0 wt % to 10 wt %, or 0.1 wt % to 5.0 wt %, or 1.0 wt % to 7.0 wt %, based on total weight of the heavy hydrocarbon feed. Sulfur will usually be present as organically bound sulfur. Examples of such sulfur compounds include the class of heterocyclic sulfur compounds such as thiophenes, tetrahydrothiophenes, benzothiophenes and their higher homologs and analogs. Other organically bound sulfur compounds include aliphatic, naphthenic, and aromatic mercaptans, sulfides, and di- and polysulfides. In some aspects involving slurry hydroconversion as the hydroconversion stage, higher sulfur feeds can be preferred, as carbon-sulfur bonds can tend to be the first to break under slurry hydroconversion conditions.
Heavy hydrocarbon feeds can be high in n-heptane asphaltenes. In some aspects, the heavy hydrocarbon feed can contain 5 wt % to 80 wt % of n-heptane asphaltenes, or 5 wt % to 60 wt %, or 5 wt % to 50 wt %, or 20 wt % to 80 wt %, or 10 wt % to 50 wt %, or 20 wt % to 60 wt %. In aspects where the heavy hydrocarbon feed includes a portion of a bitumen formed by conventional paraffinic froth treatment of oil sands, the heavy hydrocarbon feed can contain 10 wt % to 30 wt % of asphaltenes.
Still another method for characterizing a heavy hydrocarbon feed is based on the Conradson carbon residue of the feedstock, or alternatively the micro carbon residue content. The Conradson carbon residue/micro carbon residue content of the feedstock can be 5.0 wt % to 50 wt %, or 5.0 wt % to 30 wt %, or 10 wt % to 40 wt %, or 20 wt % to 50 wt %.
In various aspects, one type of upstream handling of a heavy hydrocarbon feed can correspond to addition of an extraction site diluent to form an initial feed. Adding diluent at the extraction site and/or froth treatment site can facilitate transport of the initial feed to the location of the reaction system for forming the partially processed heavy hydrocarbon product. The amount of extraction site diluent present in the initial feed can vary depending on a variety of factors. One consideration can be the amount of extraction site diluent that is needed to transport the initial feed from the extraction site (optionally including a froth treatment site) to the location of the hydroconversion process. A second consideration can be the amount of transport diluent that is desired in the final blended product, to facilitate transport of the final blended product from the location of the reaction system to a destination (such as a refinery) for the final blended product.
In some aspects, the amount of extraction site diluent present in the initial feed can be greater than the amount of transport diluent desired in the final blended product. In such aspects, an initial separation can be performed on the initial feed to remove at least a portion of the extraction site diluent, so that the amount of extraction site diluent remaining with the heavy hydrocarbon feed after the initial separation is roughly less than or equal to the target amount of transport diluent for the final blended product. In other aspects, the target amount of transport diluent may be greater than the amount of extraction site diluent that is needed to move the initial feed from the extraction site to the location of the reaction system. For example, if a dedicated pipeline is available for moving feed from the extraction site to the location of the reaction system, it may be feasible to operate such a pipeline at a higher target kinematic viscosity and/or a low target API gravity, so that a reduced or minimized amount of diluent is needed to move the initial feed to the location of the reaction system. In such aspects, the amount of extraction site diluent can be reduced to any convenient level, such as including no extraction site diluent. This can reduce or minimize the need to perform an atmospheric separation, or can alternatively simplify the atmospheric separation, as the atmospheric overhead will contain a reduced or minimized amount of diluent, such as possibly no diluent. Alternatively, it may be more convenient to increase the amount of extraction site diluent to match the target amount of transport diluent. For example, adding sufficient extraction site diluent to also satisfy the target amount of transport diluent could avoid the need to have a diluent blending facility at both the extraction site and at the location of the reaction system.
In aspects where all of the heavy hydrocarbon feed is processed in the reaction system, the amount of transport diluent that is needed in the final blended product can be reduced or minimized. This is due in part to the reduced API gravity and/or reduced viscosity of the hydroconverted effluent. For example, by performing hydroconversion on a resid portion of the heavy hydrocarbon feed, a hydroconverted effluent can be formed with a substantially increased API gravity and/or substantially reduced kinematic viscosity. This results in a final blended product with an increased API gravity and/or reduced kinematic viscosity. In some aspects, the hydroconverted effluent can increase the API gravity of the final blended product by a sufficient amount so that substantially no transport diluent is needed to achieve a desired pipeline specification and/or other transport specification. In other aspects, a reduced or minimized amount of transport diluent can be needed.
In other aspects, the heavy hydrocarbon feed can be split so that a bypass portion of the heavy hydrocarbon feed is introduced into the final blended product without further processing. In such aspects, a first portion of the heavy hydrocarbon feed is processed in the reaction system (i.e., separated to allow a resid fraction to be exposed to hydroconversion conditions). In such aspects, due to the presence of the bypass fraction, at least some transport diluent may be present in the final blended product. However, combining the hydroconverted effluent with the bypass portion can allow for an unexpectedly large reduction in the amount of transport diluent that is needed. For example, the first portion of the heavy hydrocarbon feed can be separated to form a distillate and vacuum gas oil fraction that is not hydroconverted, and a resid fraction that is exposed to hydroconversion conditions to form a hydroconverted effluent. The hydroconverted effluent can then be combined with the distillate and vacuum gas oil fraction that is not hydroconverted. In some aspects, this intermediate blend can have an API gravity that is greater than the target API gravity for the final blended product. In such aspects, additional extraction site diluent can be removed from the bypass portion while still achieving the desired transport standard. Alternatively, in aspects where the amount of transport diluent is greater than the amount of extraction site diluent, the amount of excess extraction site diluent can be reduced.
Feedstocks—Feeds with Increased Particle Content
In addition to the above properties, another consideration for a heavy hydrocarbon feedstock is the particle content. For crude oils derived from conventional extraction sites, the particle content of the crude oil is typically low. However, an increasing proportion of crude oil production corresponds to non-traditional crudes, such as crude oils derived from oil sands. Initial extraction of non-traditional crudes can present some additional challenges. For example, during mining or extraction of oil sands, a large percentage of non-petroleum material (such as sand) is typically included in the raw product.
The particle content and/or content of other non-petroleum materials of oil sands can be quite large, corresponding to 30 wt % or more of the product. An initial reduction in the particle content can be performed by first mixing the raw product with water. Air is typically bubbled through the water to assist in separating the bitumen from the non-petroleum material. This will remove a large proportion of the solid, non-petroleum material in the raw product. However, smaller particles of non-petroleum particulate solids will typically remain with the oil phase at the top of the mixture. This top oil phase is sometimes referred to as a froth. The particles in this froth can still correspond to 5.0 wt % or more of the froth, or 10 wt % or more, such as up to 20 wt % or possibly still higher.
Separation of the smaller non-petroleum particulate solids can be achieved by adding an extraction solvent to the froth of the aqueous mixture. This is referred to as a froth treatment. Examples of froth treatments include paraffinic froth treatment (PFT) and naphthenic froth treatment (NFT). For paraffinic froth treatment, typical solvents include isopentane, pentane, and other light paraffins (such as C5-C8 paraffins) that are liquids at room temperature. Other solvents such as C3-C10 alkanes might also be suitable for use as an extraction solvent for forming an asphaltene-depleted crude, depending on the conditions during the paraffinic froth treatment. For naphthenic froth treatment, a mixture of naphtha boiling range compounds can be used, where the mixture includes aromatics, naphthenes, and optionally paraffins. It is noted that the extraction solvents for paraffinic froth treatment roughly correspond to naphtha boiling range compounds as well, so that the difference between the solvents for PFT and NFT is based on compound class (aromatic, naphthene, paraffin) rather than boiling range.
During a froth treatment, adding the extraction solvent to the froth results in a two phase mixture, with the crude and the extraction solvent forming one of the phases. The smaller particulate solids of non-petroleum material are “rejected” from the oil phase and join the aqueous phase. The crude oil and solvent phase can then be separated from the aqueous phase. During conventional paraffinic froth treatment, after separation from the aqueous phase, the resulting bitumen can have a combined water and particle content of 1.0 wt % or less. Higher particle contents can be present in bitumen formed using naphthenic froth treatment.
When a paraffinic froth treatment is performed under conventional conditions, the paraffinic froth treatment can also impact the amount of asphaltenes that are retained in the bitumen product. When a paraffinic extraction solvent is added to the mixture of raw product and water, between about 30 and 60 percent of the n-heptane asphaltenes in the crude oil are typically “rejected” and lost to the water phase along with the smaller non-petroleum particulate solids. As a result, the bitumen that is separated out from the non-petroleum material after a paraffinic froth treatment corresponds to an asphaltene-depleted crude oil. By using the paraffinic froth treatment to knock out small particulate solids, the asphaltene content of the crude can be reduced or depleted by at least about 30 wt %, such as at least about 40 wt %, or at least about 45 wt %. In other words, the asphaltene-depleted crude will have about 30 wt % less asphaltenes than the corresponding raw crude, such as at least about 40 wt %, or at least about 45 wt %. Typically, the paraffinic froth treatment will reduce or deplete the asphaltenes in the crude by about 60 wt % or less, such as about 55 wt % or less, or about 50 wt % or less. The amount of asphaltenes that are removed or depleted can depend on a variety of factors. Possible factors that can influence the amount of asphaltene depletion include the nature of the extraction solvent, the amount of extraction solvent relative to the amount of crude oil, the temperature during the paraffinic froth treatment process, and the nature of the raw crude being exposed to the paraffinic froth treatment.
In various aspects, the first step in processing a heavy hydrocarbon feed can be to fractionate at least a portion of the feed. The fractionation stage can include components for performing both an atmospheric distillation and a vacuum distillation (such as an atmospheric tower and a vacuum tower). Optionally, the fractionation stage can further include a deasphalting unit.
A first option for the fractionation stage is to determine the portion of the heavy hydrocarbon feed that is fractionated. In some aspects, substantially all of the heavy hydrocarbon feed can be fractionated. In other aspects, the heavy hydrocarbon feed can be divided so that only a portion is exposed to fractionation. In such aspects, the portion exposed to fractionation can correspond to 5 to 95 wt % of the heavy hydrocarbon feed, or 15 wt % to 95 wt %, or 20 wt % to 95 wt %, or 5 wt % to 80 wt %, or 15 wt % to 80 wt %, or 20 wt % to 80 wt %, or 30 wt % to 95 wt %, or 30 wt % to 80 wt %, or 30 wt % to 70 wt %, or 40 wt % to 95 wt %, or 40 wt % to 80 wt %, or 40 wt % to 70 wt %, or 30 wt % to 50 wt %, or 50 wt % to 70 wt %. The remaining portion of the feed can be blended with one or more fractionated portions and/or hydroconverted effluent portions to form a final blend.
After determining the portion of the heavy hydrocarbon feed to fractionate, the heavy hydrocarbon feed can undergo an atmospheric distillation or separation. In some aspects, this can correspond to fractionation in an atmospheric distillation tower. In other aspects, a flash separation could be performed, or another convenient type of separation. The atmospheric separation can form at least one naphtha and/or distillate fuel boiling range fraction, and a bottoms fraction with a T10 distillation point of 343° C. or more, or 371° C. or more.
The bottoms fraction from the atmospheric separation can then be passed to a vacuum distillation tower to form at least one vacuum gas oil fraction and a vacuum resid fraction. In some aspects, the vacuum distillation tower can be operated with a conventional cut point for forming the vacuum resid fraction, such as forming a vacuum resid fraction with a T10 distillation point of 975° F. (524° C.) to 1050° F. (566° C.). In other aspects, the vacuum distillation can be operated to cut more deeply, so that the T10 distillation point of the vacuum resid is 1050° F. (566° C.) or higher, or 575° C. or higher, or 585° C. or higher, such as up to 600° C. or possibly still higher. Increasing the cut point for the vacuum resid can reduce the volume of resid that is subsequently passed into the hydroconversion stage. In some aspects, the cut point for the vacuum distillation can be selected so that the fraction passed into the hydroconversion stage corresponds to 50 wt % or less of the portion of the heavy hydrocarbon feed that is passed into the stages for separation based on boiling point, or 45 wt % or less, or 40 wt % or less, or 35 wt % or less, such as down to 30 wt % or possibly still lower. In some optional aspects, a portion of the vacuum resid can be passed instead into a partial oxidation reactor to assist with hydrogen generation for the hydroconversion stage.
In some aspects where a higher cut point is used for forming the vacuum resid, the percentage of the vacuum resid that boils at 566° C. or higher can correspond to 50 wt % or more of the vacuum resid fraction, or 60 wt % or more, or 80 wt % or more, or 90 wt % or more, such as up to having substantially all of the vacuum resid fraction correspond to 566° C.+ components. Additionally or alternately, the percentage of the vacuum resid that boils at 524° C. or more can correspond to 90 wt % or more of the vacuum resid fraction, or 95 wt % or more, such as up to having substantially all of the vacuum resid fraction correspond to 524° C.+ components.
A full range vacuum gas oil can include the final overhead or “distillate” cut that is produced from a vacuum distillation tower. When performing a vacuum distillation, the quality of the separation at the final cut point between the “distillate” and the vacuum tower bottoms can be more difficult to control. Due to the properties of 538° C.+ petroleum fractions, or 566° C.+ petroleum fractions, the final “distillate” cut of vacuum gas oil can typically included 5.0 wt % to 10 wt % of components that have a boiling range of 1000° F. (538° C.) to 1200° F. (649° C.), or 1000° F. (538° C.) to 1150° F. (621° C.). Additionally or alternately, the final “distillate” cut can include 1.0 wt % to 6.0 wt % of components having a boiling range of 1050° F. (566° C.) to 1200° F. (649° C.), or 1050° F. (566° C.) to 1150° F. (621° C.), or 1050° F. (566° C.) to 1100° F. (593° C.). These higher boiling components can become entrained in the vapor that is formed in the reboiler for the vacuum tower, resulting in exit of such higher boiling components as part of the vacuum gas oil. These components represent the highest boiling components that can exit the vacuum tower as part of a distillate cut.
Due to the above difficulties with separating the final distillate cut from the vacuum tower bottoms, a final blended product (or heavy hydrocarbon product) as described herein can include a limited amount of components with a distillation point between 566° C. and 621° C., or between 566° C. and 593° C. Such high boiling components can be included in the heavy hydrocarbon product due to being present in either the virgin vacuum gas oil or the hydroconverted gas oil that is blended together to make the heavy hydrocarbon product. However, based on the exclusion of vacuum resid or unconverted oil in the heavy hydrocarbon product, the amount of components having a distillation point of 621° C. or more, or 593° C. or more, can be limited, as such components are not as susceptible to being entrained as part of a vacuum distillate fraction. Depending on the aspect, the heavy hydrocarbon product can include 0.1 wt % or less (or 0.05 wt % or less) of 649° C.+ components, or 0.1 wt % or less (or 0.05 wt % or less) of 621° C.+ components, or 0.1 wt % or less (or 0.05 wt % or less) of 593° C.+ components. This corresponds to including substantially 649° C.+ components, or substantially no 621° C.+ components, or substantially no 593° C.+ components.
In some aspects, an additional reduction in the volume of the input stream to hydroconversion can be achieved by deasphalting the vacuum resid fraction. The deasphalting can be operated at high lift conditions, so that 40 wt % or more of the input stream becomes deasphalted oil, or 50 wt % or more, or 60 wt % or more, such as up to 75 wt % or possibly still higher. The deasphalter residue or rock can correspond to the remainder of the deasphalter output. The rock can be passed into the hydroconversion stage. Alternatively, a portion of the rock can be passed instead into a partial oxidation reactor to assist with hydrogen generation for the hydroconversion stage.
Other variations for fractionation of a feed can also be used. In some aspects, instead of deasphalting a vacuum bottoms fraction, deasphalting can be performed on a fraction with a broader boiling range, such as performing deasphalting on the heavy hydrocarbon feedstock or on an atmospheric bottoms fraction derived from the heavy hydrocarbon feedstock. Although this increases the volume of feed that is processed by deasphalting, such configurations can remove the need for performing vacuum fractionation. Still another alternative can be to fractionate the heavy hydrocarbon feedstock in a vacuum fractionator without performing a prior atmospheric fractionation. This type of configuration can be beneficial, for example, in configurations where the hydroconversion reaction system is sufficiently close to the extraction site that an extraction site diluent does not need to be added to the heavy hydrocarbon feed.
One method for forming an upgraded crude composition as described herein is by using a limited severity hydroconversion process to treat at least a portion of the vacuum resid boiling range components of a heavy hydrocarbon feed. An example of a suitable heavy hydrocarbon feed is a bitumen derived from western Canadian oil sands.
Slurry hydroconversion is a hydroprocessing method that can achieve high conversion of heavy hydrocarbon feeds to liquid hydrocarbons without rejecting carbon. Conventionally, slurry hydroconversion has had only limited use, due in part to difficulties in balancing the high pressure and/or high liquid residence time required to achieve high conversion while avoiding reaction conditions that result in either foaming or fouling in the reactor.
A slurry hydroprocessing reactor operates as a bubble column, so that both gas and liquid are present within the reactor volume during operation. This creates a tension during operation when managing the gas superficial velocity and the liquid superficial velocity in the reactor. If the gas superficial velocity becomes too high relative to the liquid superficial velocity, the liquid phase in the reactor can begin to foam, which quickly leads to an inability to operate effectively. Unfortunately, reducing the gas superficial velocity by reducing the rate of introduction of hydrogen treat gas leads to lower partial pressures of hydrogen, which can result in increased coke formation. Additionally, increasing the liquid superficial velocity by increasing the fresh feed rate, at constant temperature, typically results in reduced conversion.
One option for increasing the liquid superficial velocity without requiring an increase in the fresh feed rate is to recirculate a portion of the total liquid effluent back to the reactor. This can be accomplished using a pump-around recirculation loop. In this discussion, recirculation of liquid effluent portion to a reactor is defined as returning to the reactor a portion of liquid effluent that has substantially the same composition as the liquid within the reactor. In other words, the liquid effluent is not fractionated and/or chemically modified prior to returning the liquid effluent to the reactor. Recirculation of liquid effluent can improve the hydrodynamics of operation within a slurry hydroprocessing reactor. Such recirculation can reduce or minimize the potential for “foaming” in the slurry hydroconversion environment. When determining “per pass” conversion within the reactor, the reactor is defined to include any recirculation loops. Thus, liquid within a recirculation loop, by definition, is liquid that remains in the reactor. Any conversion performed on liquid that has traveled through a recirculation loop is therefore considered part of the “per pass” conversion.
In contrast to recirculation, recycle of liquid to the slurry hydroconversion reactor corresponds to recycle of a liquid fraction that has a different composition than the liquid phase in the reactor. Conventionally, however, recycle of the bottoms from a hydroconversion reaction is believed to not be beneficial when processing a heavy feedstock in a slurry hydroprocessing reaction environment. This is due in part to lowering of reactor productivity when using recycle streams that are small relative to the rate of fresh feed in the reactor. When using these relatively small recycle amounts, incorporation of a substantial amount of bottoms in the recycle can lead to increased coking. In order to avoid this coking, the temperature needs to be lowered to avoid reactor fouling, but this also requires a corresponding decrease in fresh feed rate in order to maintain a constant level of feed conversion. In order to avoid this choice between increased reactor fouling and decreased reactor productivity, conventional recycle streams for slurry hydrocracking units have focused on use of streams where 50 wt % or more of the recycle stream corresponds to vacuum gas oil boiling components (and/or other lower boiling range components).
In contrast to the above, it has been discovered that when performing conversion of a sufficiently heavy feedstock, such as a heavy hydrocarbon feedstock including more than 50 wt % of 566° C.+ components, or more than 50 wt % of 593° C.+ components, an unexpected productivity increase can be achieved by operating a slurry hydroprocessing reactor (or reaction system) with a substantial recycle of pitch or unconverted bottoms, so long as the recycle stream is also sufficiently heavy. The substantial recycle can correspond to a recycle stream having a mass flow rate corresponding to 50% or more of the mass flow rate of fresh feed delivered to the reaction system, such as 50% to 250% of the amount of fresh feed, or 50% to 200%, or 60% to 250%, or 60% to 200%. Such recycle rates correspond to a combined feed ratio of 1.5 to 3.5, or 1.5 to 3.0, or 1.6 to 3.5, or 1.6 to 3.0. Additionally, the substantial recycle can correspond to a pitch or unconverted bottoms stream that includes more than 50 wt % of 566° C.+ components, or 60 wt % or more. Optionally, the substantial recycle can correspond to a pitch or unconverted bottoms stream that includes 50 wt % or more of 593° C.+ components, or 60 wt % or more.
It has been discovered that operating with substantial pitch recycle can provide a variety of unexpected advantages when performing slurry hydroconversion on a heavy hydrocarbon feed. Such advantages can include, but are not limited to, increased reactor productivity and reducing or minimizing reactor fouling. Conventionally, it is believed that avoiding coke formation and/or fouling required reducing the concentration of 566° C.+ components when using recycle streams; removing asphaltenes from any recycle streams; or a combination thereof.
In particular, recycling pitch can unexpectedly improve reactor productivity, allowing an increase in the unit capacity at constant 524° C. total conversion. This is in contrast to conventional recycle methods, where using recycle streams containing 50 wt % or more of lower boiling components results in loss of reactor productivity (i.e., the fresh feed rate is reduced at constant temperature). For example, when operating slurry hydroconversion with pitch recycle, the amount of total conversion relative to 524° C. can be 60 wt % to 89 wt %, or 70 wt % to 89 wt %, or 60 wt % to 85 wt %, or 70 wt % to 85 wt %, or 75 wt % to 89 wt %. It is noted that the conversion at 566° C. will be higher than the conversion at 524° C. The per-pass conversion can be lower, corresponding to 60 wt % or less conversion relative to 524° C. In some aspects, the limited severity hydroconversion process can be used to treat all of the vacuum resid present in a heavy hydrocarbon feed, while in other aspects a portion of the heavy hydrocarbon feed can bypass all processing and be directly added to a final product.
Still further advantages can be realized when using slurry hydroconversion with substantial pitch recycle as a hydroconversion method for partial upgrading of heavy hydrocarbon feedstocks to produce a product that is suitable for pipeline transport (and/or another type of transport). Such advantages can include, but are not limited to, one or more of: incorporating an increased amount of vacuum gas oil and/or a reduced amount of pitch into the heavy hydrocarbon product; reducing or minimizing the amount of carbon-containing compounds requiring an alternative method of disposal or transport; and reduced incorporation of external streams into the final product for transport while still satisfying one or more target properties. Additionally or alternately, the resulting vacuum gas oil generated from slurry hydroconversion can have unexpected properties. For example, the resulting vacuum gas oil can have an unexpectedly high content of n-pentane insolubles, as determined according to the method described in ASTM D893.
Other potential advantages of the partially upgraded heavy hydrocarbon product can be related to the resulting product quality. By using hydroconversion for processing of the vacuum bottoms from the heavy hydrocarbon feed, conversion can be performed on the vacuum bottoms while reducing or minimizing coke formation. For example, processing the vacuum bottoms in a thermal process such as coking can result in formation of 20 wt % or more of coke relative to the 566° C.+ portion of the vacuum bottoms, or 30 wt % or more. Under conventional methods where the vacuum bottoms are at least partially incorporated into a synthetic crude product, such vacuum bottoms are often processed in a refinery by coking. By contrast, the pitch or unconverted bottoms from hydroconversion as described herein can correspond to 15 wt % or less of the 566° C.+ portion, or 10 wt % or less. Thus, by using hydroconversion, additional liquid products are formed in the hydroconversion reactor, in place of the coke that would be reformed by processing the 566° C.+ portion at a conventional refinery. Additionally, the transport of 566° C.+ material by pipeline is avoided, so that the use of pipeline capacity for transporting material that will become coke is reduced or minimized.
In various aspects, one of the characteristics of a vacuum gas oil fraction generated by the methods described herein is the presence of an unexpected quantity of n-pentane insolubles. Conventionally, vacuum gas oil fractions are expected to have an n-pentane insolubles content on the order of a few parts per million. Virgin vacuum gas oil fractions generally do not contain n-pentane insolubles. For vacuum gas oil fractions formed by cracking or other processing, a goal of the cracking or other processing is typically to reduce, minimize, or avoid production of such n-pentane insolubles. This is achieved, for example, based on a combination of selecting suitable feeds and performing the cracking/other processing at sufficiently severe conditions. By contrast, for a vacuum gas oil fraction generated by slurry hydroconversion of a sufficiently heavy feed with a sufficient amount of heavy recycle, the n-pentane insolubles content can be 0.5 wt % or more. For example, the n-pentane insolubles content (determined according to the method described in ASTM D4055) can be from 0.5 wt % to 5.0 wt %, or 1.0 wt % to 5.0 wt %, or 2.0 wt % to 5.0 wt %.
Without being bound by any particular theory, it is believed that the presence of an elevated amount of n-pentane insolubles is due in part to the heavy nature of the feed, the heavy nature of the recycle stream, and the reduced per-pass conversion. This combination of features is believed to allow for substantial primary cracking while reducing or minimizing secondary cracking. As a result, compounds with a boiling point of 1050° F.+ are effectively converted to 1050° F.− compounds. A portion of these converted 1050° F.− compounds correspond to n-pentane insolubles. However, under the conditions described herein, where the slurry hydroconversion is performed using substantial recycle of a heavy recycle stream, secondary cracking of these 1050° F.− compounds is reduced or minimized. This allows n-pentane insolubles to avoid secondary cracking in an unexpectedly high amount, so that an increased amount of n-pentane insolubles are retained in the vacuum gas oil.
In some aspects, the portion of the feed that is exposed to the hydroconversion conditions can be separated from the feed by performing a separation based on boiling point. For example, a vacuum distillation tower can be used to separate at least a vacuum resid boiling range portion of the feed from another portion of the feed. Alternatively, a series of flash separators could be used to isolate a fraction including a vacuum resid boiling range portion. In other aspects, the vacuum resid portion of the feed that is exposed to hydroconversion can correspond to a fraction that is formed by solvent deasphalting. In such aspects, at least a portion of the feed can be deasphalted, and at least a portion of the residue or rock from deasphalting can be exposed to the limited severity hydroconversion process. The deasphalter rock from solvent deasphalting corresponds to a raffinate from the solvent deasphalting process. In still other aspects, a combination of boiling point separation and solvent deasphalting can be used to form a vacuum resid portion for hydroconversion.
It has been discovered that performing limited hydroconversion on the vacuum resid portion of a heavy hydrocarbon feed, and then recombining the hydroconverted liquid effluent with the lower boiling portions of the feed, can result in a processed heavy hydrocarbon product suitable for pipeline transport while requiring a reduced or minimized amount of transport diluent to meet pipeline transport specifications, such as a processed heavy hydrocarbon product including 20 wt % or less transport diluent. It is noted that the pitch or bottoms fraction from the limited hydroconversion is not recombined. Additionally, the vacuum gas oil portion of the processed heavy hydrocarbon product can correspond to an unexpectedly high weight percentage of the product. Additionally, in some aspects (such as aspects involving slurry hydroprocessing) the systems and methods can avoid the need for including a separate particle removal step prior to hydroprocessing. In some optional aspects, the systems and methods can be used in combination with a modified paraffinic froth treatment that allows for increased recovery of hydrocarbons by increasing the asphaltenes retained in the bitumen.
In some aspects, increasing the amount of the vacuum gas oil relative to the amount of higher boiling components can correspond to forming a partially upgraded heavy hydrocarbon product containing 50 wt % or more vacuum gas oil, or 55 wt % or more vacuum gas oil, or 60 wt % or more vacuum gas oil, such as up to 75 wt % vacuum gas oil or possibly still higher. Additionally, the partially upgraded heavy hydrocarbon product can include 5.0 wt % or less of 593° C.+ components, or 3.0 wt % or less, such as down to substantially no 593° C.+ components. Optionally, the partially upgraded heavy hydrocarbon product can include 5.0 wt % or less of 566° C.+ components, or 3.0 wt % or less, such as down to substantially no 566° C.+ components.
In other aspects, increasing the amount of vacuum gas oil relative to the amount of higher boiling components can be used to enable a configuration where a substantial portion of the heavy hydrocarbon feed (optionally after solvent removal) is passed into the partially upgraded heavy hydrocarbon product without further processing. In such aspects, the heavy hydrocarbon feed is split into at least two portions. A second portion of the initial feed is blended into the final product without passing through a solvent separation, boiling point separation, or other separation stage; and without passing through a feed conversion stage (such as a hydroconversion stage or a coking stage). The first portion of the feed, corresponding to 5 wt % to 95 wt % of the initial feed, or 15 wt % to 95 wt %, or 20 wt % to 95 wt %, or 5 wt % to 80 wt %, or 15 wt % to 80 wt %, or 20 wt % to 80 wt %, is separated and processed as described herein, including processing of at least a 566° C.+ portion of the feed under hydroconversion conditions with a net conversion of 60 wt % to 89 wt % relative to 524° C. In some preferred aspects, the first portion of the initial feed can correspond to 30 wt % to 95 wt % of the initial feed, or 30 wt % to 80 wt %, or 30 wt % to 70 wt %, or 40 wt % to 95 wt %, or 40 wt % to 80 wt %, or 40 wt % to 70 wt %, or 30 wt % to 50 wt %, or 50 wt % to 70 wt %. By not including the pitch from this hydroconversion in the final product, the amount of the heavy hydrocarbon feed blended into the final product can be increased or maximized. This can allow a partially upgraded heavy hydrocarbon product to be formed that is suitable for transport while reducing or minimizing the amount of the initial feed that is processed. This can substantially reduce both the capital costs and the processing costs for generating a product suitable for transport while also maintaining an increased amount of vacuum gas oil in the product. Additionally, by avoiding addition of pitch to the partially upgraded heavy hydrocarbon product, the need to remove particles can be reduced or minimized. To the degree particles are present in the heavy hydrocarbon feed, such particles can be segregated into the pitch during the limited hydroconversion. It is noted that including a bypass portion of the heavy hydrocarbon feed in the partially upgraded heavy hydrocarbon product results in a composition that includes a vacuum bottoms portion, and therefore is not a “bottomless” crude.
Preparing heavy hydrocarbon feeds for pipeline transport often involves achieving target values for a plurality of separate properties. First, after processing to prepare for transport, the viscosity of the resulting upgraded product needs to be suitable or roughly suitable for pipeline transport. This can correspond to, for example, having a kinematic viscosity at 7.5° C. of 400 cSt or less, or 360 cSt or less, or 350 cSt or less, such as down to 250 cSt or possibly still lower. Second, the density of the heavy hydrocarbon product needs to be suitable or roughly suitable for pipeline transport. This can correspond to, for example, having an API Gravity of 18° or more, or 19° or more. Third, the particulate content of the heavy hydrocarbon product needs to be sufficiently low. Fourth, an olefin content of the heavy hydrocarbon product also needs to be sufficiently low, such as having an olefin content of 1.0 wt % or less.
Conventionally, a target kinematic viscosity and a target density are achieved in part by blending a heavy hydrocarbon feed with a suitable transport diluent, such as a naphtha boiling range diluent. While this is effective, addition of a sufficient amount of transport diluent can present a variety of challenges. For example, when attempting to add diluent to native bitumen, the amount of transport diluent required to meet both the kinematic viscosity and density requirements is usually substantial, corresponding to 30 vol % or more of the final product suitable for pipeline transport. The large amount of transport diluent required is due in part to the fact that the amount of diluent needed to achieve the kinematic viscosity requirement is typically substantially greater than the amount of transport diluent needed to achieve the density requirement. In various aspects, a goal of making a partially upgraded heavy hydrocarbon product can be to reduce the amount of giveaway in density.
With regard to particulate content, some conventional methods of processing mined tar sands involve an initial processing step to reject particles, such as performing a froth treatment. Even after such treatment (such as when a naphthenic froth treatment is used), a particle separation step may be required prior to attempting pipeline transport. In other aspects, such as when a paraffin froth treatment is used, the conditions used for rejection of particles tend to also lead to rejection of substantial portions of the asphaltenes present in the tar sands. This rejection of asphaltenes represents a loss of hydrocarbon yield relative to the original hydrocarbon content of the tar sands. The rejection of the asphaltenes also reduces or minimizes the ability to use the resulting bitumen for production of asphalt products.
In various aspects, a processing system including at least a separation stage and a hydroconversion stage can be used to provide an improved method for preparing heavy hydrocarbons for pipeline transport. The separation stage can correspond to an atmospheric separator (such as an atmospheric distillation tower or flash separator), a vacuum separator (such as a vacuum distillation tower), a solvent deasphalter, or a combination thereof. The hydroconversion stage can correspond to a slurry hydroprocessing stage, an ebullating bed hydroprocessing stage, a moving bed reactor stage, or another type of hydroconversion stage that allows for on-line catalyst withdrawal and replacement. When a boiling point separation is performed, at least one separation stage can be used to separate out a portion of any diluent present in the initial feedstock, such as separating out up to substantially all of the diluent present in the initial feedstock. In aspects where a vacuum distillation is included in the separation stage, the vacuum distillation stage can be used to cut deeply, so as to reduce or minimize the volume of feed passed to hydroconversion. For example, if the input to the vacuum distillation is a bottoms product from an atmospheric distillation, the vacuum distillation can cut deeply into the bottoms product. This can reduce or minimize the amount of vacuum resid that is subsequently processed. The vacuum resid (or at least a portion thereof) is then passed into a limited severity hydroconversion stage. Optionally, in addition to and/or instead of deeply cutting into the atmospheric bottoms, the vacuum resid can be deasphalted to produce deasphalted oil and rock. In such aspects, the deasphalter rock can be used as the feed to the hydroconversion stage instead of the vacuum tower bottoms. Yet another option can be to use the deasphalter as the primary separator in the separation stage, rather than using a fraction from a distillation tower as the feed to the deasphalter.
In various aspects, the separation stage can be used to form a fraction comprising a vacuum resid portion that is then passed into the hydroconversion stage. The fraction containing a vacuum resid portion that is passed into the hydroconversion stage corresponds to 50 wt % or less of the heavy hydrocarbon feed, or 40 wt % or less, or 35 wt % or less, or 30 wt % or less, such as down to 20 wt % or possibly still lower. Optionally, the fraction containing the vacuum resid portion can have a lower API gravity than the API gravity of the heavy hydrocarbon feed.
The hydroconversion stage is operated at a net conversion of 60 wt % to 89 wt %, relative to a conversion temperature of 975° F. (524° C.), or 70 wt % to 89 wt %, or 60 wt % to 85 wt %, or 70 wt % to 85 wt %, or 75 wt % to 89 wt %. Optionally but preferably, the hydroconversion stage can correspond to a single reactor, as opposed to having a plurality of reactors arranged in series. This can reduce or minimize the likelihood of incompatibility in aspects where a recycle stream is used as part of the input flow to the hydroconversion stage. It is noted that a plurality of reactors can be used in parallel to provide a desired total capacity for processing an input flow using hydroconversion stages with single reactors. More generally, any convenient combination of reactors in parallel and/or in series can be used. In some aspects, the net conversion can substantially correspond to the per-pass conversion in the reactor. In other aspects, a portion of the pitch or unconverted bottoms from the hydroconversion stage can be recycled. In such aspects, the per-pass conversion can be significantly lower, such as having a per-pass conversion of 60 wt % or less, or 50 wt % or less, or 40 wt % or less, relative to 524° C. or alternatively relative to 566° C. The amount of recycle can correspond to from 50 wt % to 250 wt %, or 60 wt % to 250 wt %, or 50 wt % to 200 wt %, or 60 wt % to 200 wt %, of the flow of fresh vacuum bottoms (and/or other fraction) into the hydroconversion stage. This corresponds to a combined feed ratio of 1.5 to 3.5, or 1.6 to 3.5, or 1.5 to 3.0, or 1.6 to 3.0.
The hydroconverted effluent from the hydroconversion stage can include a variety of fractions, including a hydroconverted naphtha fraction, a hydroconverted distillate fraction, a hydroconverted vacuum gas oil fraction, and a pitch fraction. The hydroconverted distillate fraction, the hydroconverted vacuum gas oil fraction, and the pitch fraction correspond to a 177° C.+ portion of the hydroconverted effluent. In some aspects, the nitrogen content of this 177° C.+ portion of the hydroconverted effluent can be at least 75 wt % of the nitrogen content of the fresh feed into the hydroconversion stage, or at least 90 wt % of the nitrogen content of the fresh feed.
In some aspects, the separation used to form the pitch or unconverted oil fraction from the hydroconversion stage effluent can be configured so that more than 50 wt % of the recycled pitch corresponds to 566° C.+ components, or 60 wt % or more, or 70 wt % or more, such as up to having substantially all of the recycle pitch correspond to 566° C.+ components. Operating with pitch recycle can potentially provide a variety of benefits. In some aspects, by using a pitch recycle stream corresponding to more than 50 wt % of 566° C.+ material while allowing vacuum gas oil to exit after once-through processing, the residence time of heavier components is increased while maintaining a lower residence time for vacuum gas oil in the feed. It is believed that this contributes to forming a hydroconversion effluent that is enriched in vacuum gas oil compounds, as overcracking of the vacuum gas oil compounds is reduced or minimized. In some aspects, without being bound by any particular theory, it is believed that by increasing pitch recycle while maintaining a relatively low total conversion, the amount of aromatic compounds present in the slurry hydroconversion effluent can be increased, resulting in improved solvency for the final heavy hydrocarbon product. This can reduce, minimize, or prevent asphaltene precipitation when mixing the hydroconversion effluent with virgin distillate and/or virgin vacuum gas oil fractions, such as when forming a heavy hydrocarbon product. This can work in combination with avoiding overcracking of the vacuum gas oil to reduce or minimize the amount of additional naphtha that is needed as a transport diluent.
Still another potential benefit can be achieved by using a combination of a sufficiently heavy feed with a sufficiently high amount of pitch recycle where the pitch recycle is also sufficiently heavy. For example, by using a fresh feed containing 50 wt % or more of 566° C.+ components, a pitch recycle mass flow rate corresponding to 50 wt % to 250 wt % of the fresh feed mass flow rate, and a pitch recycle containing more than 50 wt % 566° C.+ components, an unexpected increase in reactor productivity can be achieved. This can provide additional capacity for processing bitumen (and/or other heavy hydrocarbon feeds) relative to the size of the reactor and/or allow a reactor to operate at higher conversion. Additionally or alternately, by using high pitch recycle to enable additional conversion of 566° C.+ components while reducing or minimizing secondary cracking, the amount of light gas (C4− components) that is generated can be reduced.
In some aspects, the fresh feed to the hydroconversion stage can include 60 wt % or more of 566° C.+ components, or 75 wt % or more, or 90 wt % or more, such as having substantially all of the fresh feed to the hydroconversion stage correspond to 566° C.+ material. This can provide further benefits when attempting to form a partially upgraded heavy hydrocarbon product with an increased vacuum gas oil content. By reducing or minimizing the amount of vacuum gas oil passed into the hydroconversion stage as part of the fresh feed, overcracking of vacuum gas oil products to lower boiling compounds can be reduced or minimized. In aspects where pitch recycle is also used, additional benefits in avoiding overcracking can be achieved by using a pitch recycle stream including more than 50 wt % of 566° C.+ components, or 60 wt % or more, or 70 wt % or more, such as up to having substantially all of the pitch recycle stream correspond to 566° C.+ material.
In various aspects, the amount of pitch passed into a partial oxidation stage for conversion into hydrogen and carbon can correspond to 10 wt % or less of the initial heavy hydrocarbon feed, or 7.5 wt % or less, or 5.0 wt % or less, such as down to 2.0 wt % or possibly still lower.
It has been discovered that by reducing or minimizing the amount of the heavy hydrocarbon feed that is exposed to hydroconversion conditions, and by performing limited conversion during hydroconversion, a hydroconversion product can be produced with desirable properties. For example, the hydroconversion product can be blended together with the remaining, non-hydroconverted portion of the heavy hydrocarbon feed to form a processed heavy hydrocarbon product. Due to the hydroconversion of the bottoms of the heavy hydrocarbon feed under mild hydroconversion conditions, the resulting processed heavy hydrocarbon product can be compatible with pipeline transport standards with addition of little or possibly no additional transport diluent. It is noted that the naphtha boiling range fraction of the hydroconversion effluent can have a similar boiling range to a transport diluent. When the naphtha boiling range fraction from the hydroconversion effluent is added to the blend corresponding to the processed heavy hydrocarbon product, the naphtha from the hydroconversion effluent can correspond to 3.0 wt % to 15 wt % of the weight of the blend, or 5.0 wt % to 15 wt %, or 3.0 wt % to 10 wt %, or 5.0 wt % to 10 wt %. This naphtha boiling range fraction can act in a similar manner to a transport diluent, even though it is part of the hydroconverted product for transport. Thus, even though there may be no added transport diluent, a transport diluent can be present in the final blend based on inclusion of the naphtha boiling range fraction from the hydroconversion effluent. In this discussion, added transport diluent/additional transport diluent is defined as a naphtha boiling range fraction, not derived from the hydroconversion effluent that is added to the processed heavy hydrocarbon product.
In various aspects, the amount of diluent in a processed heavy hydrocarbon product (as described herein) can be 20 wt % or less, or 15 wt % or less, or 10 wt % or less, such as down to 3.0 wt % or possibly still lower. In some aspects, this can correspond to forming a blend (i.e., the processed heavy hydrocarbon product) that includes 10 wt % or less of additional transport diluent, or 5.0 wt % or less, or 3.0 wt % or less, such as down to having substantially no added transport diluent. In this discussion, a processed heavy hydrocarbon product that includes substantially no added transport diluent corresponds to a product that includes less than 1.0 wt % of added transport diluent.
In order to achieve a desired level of diluent in the partially upgraded heavy hydrocarbon product, a sufficient amount of diluent can be removed from the heavy hydrocarbon feed during the initial separation step(s). For example, when upgrading a heavy hydrocarbon feed for transport, substantially all of the naphtha in the feed can correspond to extraction site diluent. An initial boiling point separation can be used to remove such naphtha, so that any distillate and/or vacuum gas oil boiling range fractions for incorporation into the final product blend can have a reduced or minimized content of 177° C.− material. For example, during an initial separation stage, a boiling point separation can be used to form a fresh feed fraction for use as feed to the slurry hydroconversion stage; a diluent fraction including 177° C.− material; and one or more additional fractions containing 177° C.+ material for incorporation into the final blended product. The amount of 177° C.− components in the one or more additional fractions can correspond to 5.0 wt % or less of the one or more additional fractions, or 3.0 wt % or less, or 1.0 wt % or less.
In various aspects, the heavy hydrocarbon product can correspond to a blend that is formed by processing two or more portions of the initial heavy hydrocarbon feed in different manners. For example, in some aspects, prior to fractionation, the heavy hydrocarbon feed can be split into a plurality of portion. In such aspects, at least one of the portions (such as a second portion) can be introduced into the final blend without further processing, while at least a first portion can be exposed to separation and limited hydroconversion (or at least part of the portion). A liquid effluent portion of the hydroconversion products can then be incorporated into the final blend. In other aspects, substantially all of the heavy hydrocarbon feed can be fractionated into a plurality of fractions. In such aspects, at least one lighter fraction can be introduced into the final blend without further processing, while a second portion can be exposed to hydroconversion conditions. A liquid effluent portion of the hydroconversion products can then be incorporated into the final blend. It is noted that the portion of the hydroconversion products that is incorporated into the final blend can optionally (but preferably) correspond to a portion that undergoes further processing. For example, the portion of the hydroconversion products that is incorporated into the final blend can include naphtha and/or distillate portions that are exposed to stabilization (or other hydrotreatment) conditions prior to incorporation into the final blend.
In some aspects, the heavy hydrocarbon product can include 40 wt % or more of a 343° C.-566° C. fraction, or 50 wt % or more, or 60 wt % or more, such as up to 70 wt % or possibly still higher. Such aspects can correspond to a partially upgraded heavy hydrocarbon product that contains an elevated amount of vacuum gas oil. In some aspects, the processed heavy hydrocarbon product can correspond to a “bottomless” crude. A bottomless crude refers to a crude oil fraction that includes a reduced or minimized amount of vacuum resid boiling range components. For example, a bottomless crude can contain 3.0 wt % or less of 593° C.+ components, or 1.0 wt % or less, such as down to substantially no 593° C.+ components (i.e., 0.1 wt % or less). Additionally or alternately, a bottomless crude can contain 5.0 wt % or less of 566° C.+ components, or 3.0 wt % or less, or 1.0 wt % or less, such as down to substantially no 566° C.+ components.
After forming the final blend, an additional distillation can optionally be performed to reduce the amount of transport diluent. Additionally or alternately, additional transport diluent can optionally be added as the final blend is formed. The processed heavy hydrocarbon product can correspond to this final blend after any optional additional distillation and/or addition of transport diluent.
In some optional aspects, the heavy hydrocarbon feed that is passed into the distillation stage corresponds to a heavy hydrocarbon feed that is formed by processing of oil sands using a froth treatment. The froth treatment can correspond to a paraffinic froth treatment, a naphthenic froth treatment, or another type of froth treatment. It is noted that a heavy hydrocarbon feed can also be generated from oil sands by using steam and/or solvent to enhance extraction from the oil sands.
In some optional aspects, the distillation stage can further include performing deasphalting on the atmospheric resid and/or vacuum resid formed during vacuum distillation. In other optional aspects, deasphalting can be performed on the feed without performing prior fractionation. In such aspects, at least a portion of the input flow to the hydroconversion stage (such as a slurry hydroprocessing stage) can correspond to a rock fraction formed from the deasphalting.
Slurry hydroprocessing is an example of a type of hydroconversion that can be performed under limited severity conditions and that can also allow for withdrawal and addition of catalyst during operation of the hydroconversion process. In a reaction system, slurry hydroprocessing can be performed by processing a feed in one or more slurry hydroprocessing reactors. In some aspects, the slurry hydroprocessing can be performed in a single reactor, or in a group of parallel single reactors. The reaction conditions in a slurry hydroconversion reactor can vary based on the nature of the catalyst, the nature of the feed, the desired products, and/or the desired amount of conversion.
With regard to catalyst, several options are available. In some aspects, the catalyst can correspond to one or more catalytically active metals in particulate form and/or supported on particles. In other aspects, the catalyst can correspond to particulates that are retained within the heavy hydrocarbon feed after using a froth treatment to form the feed. In still other aspects, a mixture of catalytically active metals and particulates retained in the heavy hydrocarbon feed can be used.
In aspects where a catalytically active metal is used as the catalyst, suitable catalyst concentrations can range from about 50 wppm to about 50,000 wppm (or roughly 5.0 wt %), depending on the nature of the catalyst. Catalyst can be incorporated into a hydrocarbon feedstock directly, or the catalyst can be incorporated into a side or slip stream of feed and then combined with the main flow of feedstock. Still another option is to form catalyst in-situ by introducing a catalyst precursor into a feed (or a side/slip stream of feed) and forming catalyst by a subsequent reaction.
Catalytically active metals for use in slurry hydroprocessing/hydroconversion can include those from Groups 4-10 of the IUPAC Periodic Table. Examples of suitable metals include iron, nickel, molybdenum, vanadium, tungsten, cobalt, ruthenium, and mixtures thereof. The catalytically active metal may be present as a solid particulate in elemental form or as an organic compound or an inorganic compound such as a sulfide or other ionic compound. Metal or metal compound nanoaggregates may also be used to form the solid particulates.
A catalyst in the form of a solid particulate is generally a compound of a catalytically active metal, or a metal in elemental form, either alone or supported on a refractory material such as an inorganic metal oxide (e.g., alumina, silica, titania, zirconia, and mixtures thereof). Other suitable refractory materials can include carbon, coal, and clays. Zeolites and non-zeolitic molecular sieves are also useful as solid supports. One advantage of using a support is its ability to act as a “coke getter” or adsorbent of asphaltene precursors that might otherwise lead to fouling of process equipment.
In some aspects, it can be desirable to form catalyst for slurry hydroprocessing in situ, such as forming catalyst from a metal sulfate catalyst precursor or another type of catalyst precursor that decomposes or reacts in the hydroconversion reaction zone environment, or in a pretreatment step, to form a desired, well-dispersed and catalytically active solid particulate. Precursors also include oil-soluble organometallic compounds containing the catalytically active metal of interest that thermally decompose to form the solid particulate having catalytic activity. Other suitable precursors include metal oxides that may be converted to catalytically active (or more catalytically active) compounds such as metal sulfides.
In some aspects, the hydroconversion reactor can be configured to use particles present in the input flow to the reactor as at least a portion of the catalyst. For example, when the hydroconversion reactor corresponds to a slurry hydroprocessing reactor, substantially all of the catalyst used in the reactor can correspond to catalyst particles that are included in the input flow to the reactor and/or catalyst particles that are created in-situ within the reactor. In such aspects, one option can be to use particulates from the extraction source as at least a portion of the catalyst.
The reaction conditions within a slurry hydroprocessing reactor that correspond to a selected conversion amount can include a temperature of 400° C. to 480° C., or 425° C. to 480° C., or 450° C. to 480° C. Some types of slurry hydroprocessing reactors are operated under high hydrogen partial pressure conditions, such as having a hydrogen partial pressure of 1000 psig (6.39 MPag) to 3400 psig (23.4 MPag), for example at least 1200 psig (8.3 MPag), or at least about 1500 psig (10.3 MPag). Examples of hydrogen partial pressures can be 1000 psig (6.9 MPag) to 3000 psig (20.7 MPag), or 1000 psig (8.3 MPag) to 2500 psig (17.2 MPag), or 1500 psig (10.3 MPag) to 3400 psig (23.4 MPag), or 1000 psig (6.9 MPag) to 2000 psig (13.8 MPag), or 1200 psig (8.3 MPag) to 2500 psig (17.2 MPag). Since the catalyst is in slurry form within the feedstock, the space velocity for a slurry hydroconversion reactor can be characterized based on the volume of feed processed relative to the volume of the reactor used for processing the feed. Suitable space velocities for slurry hydroconversion can range, for example, from about 0.05 v/v/hr−1 to about 5 v/v/hr−1, such as about 0.1 v/v/hr−1 to about 2 v/v/hr−1.
In some aspects, the quality of the hydrogen stream used for slurry hydroprocessing can be relatively low. For example, in aspects where the catalyst is concentrated into the pitch and removed from the system as part of a product from a partial oxidation reactor, catalyst lifetime can be of minimal concern. This is due to the constant addition of fresh catalyst, whether in the form of particulates from the heavy hydrocarbon feed or in the form of a separately added catalyst. As a result, reaction conditions that conventionally are considered undesirable for hydroprocessing due to catalyst deactivation can potentially be used. This can potentially provide unexpected synergies when a partial oxidation reactor is used to provide at least a portion of the hydrogen for the hydroconversion process.
One example of a reaction condition that is avoided in conventional hydroprocessing is use of hydrogen streams that have relatively high concentrations of known catalyst poisons. Some catalyst poisons can correspond to catalyst poisons commonly found in recycled hydrogen treat gas streams, such as H2S, NH3, CO, and other contaminants. Other catalyst poisons can correspond to contaminants that may be present in hydrogen derived from processing of pitch in a partial oxidation reactor, such as nitrogen oxides (NOx), sulfur oxides (SOx), arsenic compounds, and/or boron compounds. In order to use hydrogen generated by partial oxidation of pitch in a conventional hydroprocessing reactor, various cleanup processes would be needed to reduce or minimize the content of various contaminants in the hydrogen treat gas. However, using a partial oxidation reactor to provide hydrogen for a slurry hydroprocessing reactor can provide the unexpected synergy of allowing at least some cleanup steps to be avoided, due to the tolerance of the slurry hydroprocessing reaction conditions for the presence of various contaminants.
In some aspects, the H2 content of the hydrogen-containing stream introduced into the slurry hydroprocessing reactor can be 90 vol % or less, or 80 vol % or less, or 60 vol % or less, such as down to 40 vol % or possibly still lower. In other aspects, the H2 content of the hydrogen-containing stream can be 80 vol % or more, or 90 vol % or more. For example, the hydrogen-containing stream can contain 80 vol % to 100 vol % H2, or 90 vol % to 100 vol %, or 80 vol % to 98 vol %, or 90 vol % to 98 vol %, or 80 vol % to 96 vol %, or 90 vol % to 96 vol %. Additionally or alternately, the combined content of H2S, CO, and NH3 in the hydrogen-containing stream can be 1.0 vol % or more, or 3.0 vol % or more, or 5.0 vol % or more, such as up to 15 vol % or possibly still higher. Further additionally or alternately, the combined content of H2, H2O, and N2 in the hydrogen-containing stream introduced into the slurry hydroprocessing reactor can be 95 vol % or less, or 90 vol % or less, or 85 vol % or less, such as down to 75 vol % or possibly still lower. For example, the combined content of H2, H2O, and N2 in the hydrogen-containing stream introduced into the slurry hydroprocessing reactor can be 75 vol % to 95 vol %.
In order to achieve various features described herein, including one or more of an unexpected increase in reactor productivity, an increased yield of vacuum gas oil yield, and/or production of a hydroconverted effluent including an unexpectedly high nitrogen content, the slurry hydroprocessing stage can be operated under a combination of conditions that allow for access to an unexpected region of the hydroprocessing phase space. This combination of conditions can include, a relatively low per-pass conversion, an elevated content of 566° C.+ material in the feed to the slurry hydroconversion stage, a recycle stream that is sufficiently large relative to the amount of fresh feed, and an elevated content of 566° C.+ material in the recycle stream.
The slurry hydroprocessing stage can be operated at a net conversion of 60 wt % to 89 wt %, relative to a conversion temperature of 524° C., or 70 wt % to 89 wt %, or 60 wt % to 85 wt %, or 70 wt % to 85 wt %, or 75 wt % to 89 wt %. Optionally but preferably, the slurry hydroprocessing stage can correspond to a single slurry hydroprocessing reactor, as opposed to having a plurality of reactors arranged in series. In some aspects, the net conversion can substantially correspond to the per-pass conversion in the slurry hydroprocessing reactor. In other aspects, a portion of the pitch or unconverted bottoms from the slurry hydroprocessing reactor can be recycled. In such aspects, the per-pass conversion can be significantly lower, such as having a per-pass conversion of 60 wt % or less, or 50 wt % or less, or 40 wt % or less, relative to 524° C. or alternatively relative to 566° C.
It is noted that reducing or minimizing the amount of vacuum gas oil that is exposed to hydroconversion while operating with pitch recycle can generate a product with increased vacuum gas oil content and reduced or minimized content of 1050° F.+(566° C.+) components. This can provide benefits in later processing. For example, it is believed that reducing or minimizing the 566° C.+ content in the processed heavy hydrocarbon product can reduce or minimize production of main column bottoms if the resulting processed heavy hydrocarbon product is used as a feed for fluid catalytic cracking.
In addition to operating at reduced conversion, the slurry hydroprocessing reactor can also perform a relatively low level of hydrodesulfurization and/or hydrodenitrogenation. In various aspects, the amount of nitrogen removal (conversion to NH3 or other light end nitrogen compounds) can correspond to 35 wt % or less of the organic nitrogen in the feed to the slurry hydroprocessing reactor, or 30 wt % or less, or 25 wt % or less, such as down to 10 wt % or possibly still lower. Additionally or alternately, the amount of sulfur removal (conversion to H2S or other light end sulfur compounds) can correspond to 90 wt % or less of the sulfur in the feed to the slurry hydroprocessing reactor, or 85 wt % or less, or 80 wt % or less, such as down to 60 wt % or possibly still lower. For example, the amount of sulfur removal can correspond to 60 wt % to 90 wt %, or 70 wt % to 85 wt %.
The per-pass conversion level for the slurry hydroprocessing reactor can be selected so that the pitch or bottoms fraction provides a sufficient amount of recycle. The amount of recycle can correspond to from 50 wt % to 250 wt % of the flow of fresh feed into the slurry hydroprocessing reactor, or 50 wt % to 200 wt %, or 60 wt % to 250 wt %, or 60 wt % to 200 wt %, or 50 wt % to 150 wt %. Additionally, the separation of the products from the slurry hydroprocessing reactor can be selected so that more than 50 wt % of the recycled pitch corresponds to 566° C.+ components, or 60 wt % or more, or 90 wt % or more. Thus, the conversion level during a single pass and the subsequent separation of the reaction products can be selected so that a) a sufficient amount of recycled pitch is available, and b) the total conversion corresponds to a target conversion of less than 90 wt % relative to 524° C. Without being bound by any particular theory, it is believed that increasing pitch recycle while maintaining a relatively low total conversion, the amount of aromatic compounds present in the slurry hydroconversion effluent can be increased, resulting in improved solvency for the final heavy hydrocarbon product. This can reduce or minimize the amount of additional naphtha (or other diluent) that is needed to allow the heavy hydrocarbon product to be suitable for pipeline transport.
An alternative way of expressing the amount of recycled pitch versus fresh vacuum bottoms can be based on a “recycled pitch ratio”. The recycled pitch ratio can also be referred to as a combined feed ratio. In this discussion, the combined feed ratio is defined, on a mass basis, as the combined amount of fresh vacuum bottoms (or alternatively deasphalter rock) plus recycled pitch, divided by the amount of fresh vacuum bottoms (or alternatively deasphalter rock). Based on this definition, the combined feed ratio has a value of 1.0 when there is no recycle. The value of the ratio increases as more pitch is recycled. When the amount of recycled pitch is equal to the amount of fresh vacuum bottoms the combined feed ratio is 2.0. The advantage of this definition for the combined feed ratio is that it is easy to understand the flow rate into the slurry hydroprocessing reactor. A ratio of 1.0 means that the reactor is sized/operated to receive only fresh feed. A ratio of 2.0 means that the reactor needs to be able to handle a feed volume that is twice the rate of fresh feed. In aspects where pitch is recycled for combination with the fresh vacuum bottoms (or alternatively deasphalter rock), the combined feed ratio can range from 1.1 to 3.5, or 1.1 to 3.0, or 1.5 to 3.5, or 1.5 to 3.0, or 1.1 to 2.5, or 1.5 to 2.5.
Without being bound by any particular theory, it is believed that using a sufficiently high amount of a sufficiently heavy recycle can reduce the formation of incompatible compounds in the reactor environment. It is believed that the formation of incompatible compounds is reduced or minimized in part by reducing exposure of lower boiling components to the reaction environment multiple times, and in part by reducing the severity (i.e., reducing the per-pass conversion) of the reaction environment.
Under conventional conditions for slurry hydroconversion of 60 wt % or more of a feedstock relative to 524° C., the fresh feed into the reaction environment can often contain a substantial portion of lower boiling compounds, such as vacuum gas oil boiling range components (343° C.-566° C. components). It is believed that additional (secondary) cracking of such vacuum gas oil boiling range compounds increases the likelihood of resid (566° C.+) components becoming incompatible with the liquid phase in the reaction environment. It is further believed that the amount of incompatible compounds generated due to overcracking of vacuum gas oil boiling range compounds within the slurry hydroprocessing reaction environment increases with increasing conversion relative to 524° C. It is believed that by increasing the amount of 566° C.+ compounds in the reaction environment, and operating at moderate per-pass conversion, the problems due to incompatibility can be reduced or minimized. This allows the reactor to be operated at increased productivity while maintaining reduced or minimized coke formation.
Due to the above combination of factors, using small recycle streams (regardless of composition) can tend to reduce the productivity of a slurry hydroprocessing reactor, or at best lead to no change in reactivity. When using a small recycle stream containing less than 40 wt % of the amount of fresh feed, at constant total conversion, the change in single-pass conversion in the reactor can be relatively small. As a result, introducing a small recycle stream does not provide a substantial reduction in the severity of the reaction environment. However, such small recycle streams typically also include previously processed vacuum gas oil boiling range components, which are then introduced into the reaction environment. It is believed that these previously processed vacuum gas oil boiling range components have an increased tendency to form incompatible compounds at a given level of conversion (or reaction condition severity). As a result, at constant fresh feed rate, the introduction of a small recycle stream is believed to result in either no impact on formation of incompatible compounds or an increase in formation of incompatible compounds. Thus, in order to avoid fouling, when using small recycle streams, the flow of fresh feed is reduced and/or large excesses of lower boiling components are included in the recycle stream.
By contrast, it has been discovered that using a substantially larger recycle stream, with a sufficiently large content of 566° C.+ components, can provide increased reactor productivity when operating at total conversions of 60 wt % to less than 90 wt % for slurry hydroconversion of a heavy hydrocarbon feed. Without being bound by any particular theory, it is believed that the productivity benefits are based on a combination of factors that allow for operation of a slurry hydroprocessing reactor in an unexpected region of the reaction condition phase space for slurry hydroconversion. First, using a sufficiently high boiling initial feed, such as a heavy hydrocarbon feed containing 50 wt % or more of 566° C.+ components, reduces or minimizes the amount of fresh feed that is susceptible to formation of incompatible compounds during a single pass through the slurry hydroconversion reactor. Second, using a recycle stream corresponding to 50 wt % or more of the fresh feed provides a sufficient amount of recycle so that the per-pass conversion can be substantially reduced. For example, by using a sufficient amount of recycle, the per-pass conversion relative to 524° C. can be lower than the net conversion relative to 524° C. by 15% or more, or 25% or more, or 30% or more, such as having a per-pass conversion that is lower than the net conversion by up to 50% or possibly still higher. By reducing the per-pass conversion (i.e., reducing the severity in the reactor), the amount of incompatible compounds generated in the reaction environment can be reduced. Third, by using a recycle stream containing more than 50 wt % of 1050° F.+ (566° C.+) components, the amount of previously processed lower boiling components introduced into the slurry hydroprocessing reaction environment can be reduced. This can further reduce or minimize generation of incompatible compounds within the reaction environment.
Based on the above factors, performing substantial recycle using a sufficiently heavy recycle stream allows for reduced formation of incompatible compounds. This reduction in formation of incompatible compounds allows the reaction system to process an unexpectedly heavy combination of feed and recycle streams while avoiding fouling and/or shutdown of the reactor due to substantial coke formation. By enabling operation in an unexpected region of the slurry hydroconversion phase space, additional benefits are also achieved. For example, by operating with a recycle stream containing a sufficiently high content of 566° C.+ components, reactor productivity is increased, as an increased percentage of the reactions within the reaction environment correspond to primary cracking of 566° C.+ compounds, as opposed to secondary cracking of 566° C.− compounds. Such secondary cracking of 566° C.− compounds is further reduced or minimized based on the lower single-pass conversion.
It is noted that the absence of any one of the multiple factors described above can inhibit or prevent the ability to access the unexpectedly desirable region of the reaction condition phase space for slurry hydroconversion. For example, if the size of the recycle stream is not sufficiently large, the reduction in per-pass conversion will not be sufficient to realize the benefits of the recycle, and instead a decrease in productivity will be observed. If the initial feedstock and/or the recycle stream does not contain a sufficiently high content of 566° C.+ material, the feed itself will contain an undesirable amount of vacuum gas oil boiling range compounds that are susceptible to overcracking to form incompatible compounds.
In addition to improving reactor productivity, operating a slurry hydroprocessing reactor with pitch recycle can potentially provide various additional benefits. For example, bottoms or pitch recycle can increase the catalyst concentration in the reactor, permitting a reduction in the catalyst make-up rate and/or higher severity operation.
Still other potential benefits can include, but are not limited to: reducing or minimizing the amount of secondary cracking of primary VGO products into incompatible paraffin side chains and aromatic cores; improving VGO quality to facilitate processing in downstream units; and/or reducing hydrogen consumption and light ends production.
After exposing the feed to slurry hydroconversion conditions in slurry hydroprocessing reactor 410, the resulting slurry hydroprocessing effluent 415 can be passed into one or more separation stages. In the example shown in
Both vapor fraction 422 and second product fraction 432 can optionally undergo further separations and/or additional processing, as desired. For example, as shown in
In the configuration shown in
After hydroconversion, a hydrotreatment stage corresponding to a stabilizer can be used to reduce the reactivity of the hydroconversion effluent. This can be achieved by performing a mild hydrotreating that allows for saturation of olefins, termination of radicals, and reaction of other high reactivity functional groups that may have formed under the slurry hydroprocessing conditions. In some aspects, a portion of the hydroconversion effluent can be exposed to stabilization, such as a naphtha portion, a distillate portion, or a combination thereof. In other aspects, the input flow to stabilization can include a portion of the vacuum gas oil fraction of the hydroconversion effluent. In yet other aspects, substantially all of the hydroconversion effluent can be passed into the stabilizer. Still another option can be to pass a portion of the unconverted distillate or vacuum gas oil from the initial feed into the stabilizer. In aspects where only a portion of the hydroconversion effluent is exposed to stabilizer hydrotreatment conditions, a remaining portion of the hydroconversion effluent can by-pass the stabilizer and then be recombined with the stabilizer effluent. The combination of the stabilizer effluent (or at least a portion thereof) with the remaining portion of the hydroconversion effluent that by-passes the stabilizer can be referred to as the stabilizer product.
The catalysts used for the stabilizing hydrotreatment can include conventional hydroprocessing catalysts, such as those that comprise at least one Group VIII non-noble metal (Columns 8-10 of IUPAC periodic table), preferably Fe, Co, and/or Ni, such as Co and/or Ni; and at least one Group VI metal (Column 6 of IUPAC periodic table), preferably Mo and/or W. Such hydroprocessing catalysts optionally include transition metal sulfides that are impregnated or dispersed on a refractory support or carrier such as alumina and/or silica. The support or carrier itself typically has no significant/measurable catalytic activity. Substantially carrier- or support-free catalysts, commonly referred to as bulk catalysts, generally have higher volumetric activities than their supported counterparts.
The catalysts can either be in bulk form or in supported form. In addition to alumina and/or silica, other suitable support/carrier materials can include, but are not limited to, zeolites, titania, silica-titania, and titania-alumina. Suitable aluminas are porous aluminas such as gamma or eta having average pore sizes from 50 to 200 Å, or 75 to 150 Å; a surface area from 100 to 300 m2/g, or 150 to 250 m2/g; and a pore volume of from 0.25 to 1.0 cm3/g, or 0.35 to 0.8 cm3/g. More generally, any convenient size, shape, and/or pore size distribution for a catalyst suitable for hydrotreatment of a distillate (including lubricant base oil) boiling range feed in a conventional manner may be used. It is within the scope of the present invention that more than one type of hydroprocessing catalyst can be used in one or multiple reaction vessels.
The at least one Group VIII non-noble metal, in oxide form, can typically be present in an amount ranging from about 2 wt % to about 40 wt %, preferably from about 4 wt % to about 15 wt %. The at least one Group VI metal, in oxide form, can typically be present in an amount ranging from about 2 wt % to about 70 wt %, preferably for supported catalysts from about 6 wt % to about 40 wt % or from about 10 wt % to about 30 wt %. These weight percents are based on the total weight of the catalyst. Suitable metal catalysts include cobalt/molybdenum (1-10% Co as oxide, 10-40% Mo as oxide), nickel/molybdenum (1-10% Ni as oxide, 10-40% Co as oxide), or nickel/tungsten (1-10% Ni as oxide, 10-40% W as oxide) on alumina, silica, silica-alumina, or titania.
In some aspects, hydrotreating conditions can include temperatures of 200° C. to 400° C., or 200° C. to 350° C., or 250° C. to 325° C.; pressures of 250 psig (1.8 MPag) to 1500 psig (10.3 MPag), or 250 psig (1.8 MPag) to 1000 psig (6.9 MPag), or 300 psig (2.1 MPag) to 800 psig (5.5 MPag); liquid hourly space velocities (LHSV) of 0.1 hr−1 to 10 hr−1; and hydrogen treat gas rates of 200 scf/B (35.6 m3/m3) to 10,000 scf/B (1781 m3/m3), or 500 (89 m3/m3) to 10,000 scf/B (1781 m3/m3). In other aspects, higher severity hydrotreating conditions may be desirable in order to further reduce the sulfur and/or nitrogen content in the hydroconverted fractions. In such aspects, a higher temperature can potentially be used, such as a temperature of 260° C. to 425° C.; and/or a higher pressure can be used, such as a pressure of 800 psig (5.5 MPag) to 2000 psig (13.8 MPag).
A variety of configurations can be used for upgrading a heavy hydrocarbon feed to be suitable for transport. The various configurations can reduce or minimize the amount of feed that requires transport by other methods. This can be accomplished using a combination of an appropriate initial separation followed by hydroconversion with limited conversion.
A heavy hydrocarbon feed 115, optionally including extraction solvent, can be passed into one or more separation stages. In the example shown in
In the example shown in
In some aspects, atmospheric separator 120 can be optional, so that the diluted bitumen/other heavy hydrocarbon feed optionally mixed with extraction site solvent is passed directly into vacuum fractionator 130. For example, in aspects where the heavy hydrocarbon feed is not mixed with extraction site diluent and/or in aspects where the extraction site diluent includes distillate and/or vacuum gas oil fractions, the heavy hydrocarbon feed may contain a reduced or minimized amount of naphtha boiling range components. While distillate boiling range components could still be separated using an atmospheric separator, it may be desirable to instead separate out the distillate fraction and the vacuum gas oil fraction in the vacuum fractionator.
The vacuum bottoms fraction 135 can then be passed into a hydroconversion stage 140. In the example shown in
In the example shown in
The pitch 149 can include substantially all of the particles that exit from hydroconversion stage 140. This can include catalyst particles (such as catalyst particles from slurry hydroconversion), particles retained in the heavy hydrocarbon feed after a froth treatment, and/or coke particles formed during hydroconversion. The pitch 149 can be passed into a partial oxidation reactor 160. By performing partial oxidation on the pitch, hydrogen can be generated to supply hydrogen stream 161 to hydroconversion stage 140. As needed, additional hydrogen can be provided, such as hydrogen from a steam methane reforming unit (not shown). The residue or slag 165 from partial oxidation reactor 160 can then be disposed of in a convenient manner, such as by sending the slag 165 to a metals reclamation stage. In various aspects, the slag 165 from partial oxidation reactor 160 corresponds to the only carbon-containing portion of heavy hydrocarbon feed 115 that requires separate transport.
The configuration shown in
An additional potential advantage of the configuration shown in
In some aspects, substantially all of the vacuum bottoms fraction is used as the feed to the hydroconversion reactor. In other aspects, such as the configuration shown in
In aspects where a bitumen with a reduced asphaltene content is used as at least a portion of the heavy hydrocarbon feed, such as a bitumen derived from a paraffinic froth treatment, the reduced asphaltene content of a bitumen (or other heavy hydrocarbon feed) can potentially limit the quality of an asphalt made from portions of the vacuum resid and/or vacuum gas oil fractions of the bitumen. One option for improving asphalt quality can be to partially oxidize the vacuum resid used for asphalt formation, such as by air blowing. For example, in an asphalt oxidation process, an asphalt feed can be preheated to a temperature from 125° C. to 300° C. The asphalt feed can then be exposed to air (or another convenient source of oxygen) in an oxidizer vessel. An example of a suitable oxidizer vessel can be a counter-current oxidizer vessel where the air travels upward through and passes through the asphalt feed as it travels downward in the vessel. The air is not only the reactant, but also serves to agitate and mix the asphalt, thereby increasing the surface area and rate of reaction. Oxygen is consumed by the asphalt as the air ascends through the down flowing asphalt. Steam or water can be sprayed into the vapor space above the asphalt to suppress foaming and to dilute the oxygen content of waste gases that are formed during the oxidation process. The oxidizer vessel is typically operated at low pressures of 0 to 2 barg. The temperature of the oxidizer vessel can be from 150° C. to 300° C., or from 200° C. to 270° C., or from 250° C. to 270° C. In some aspects, the temperature within the oxidizer can be at least 10° C. higher than the incoming asphalt feed temperature, or at least 20° C. higher, or at least 30° C. higher. The low pressure off-gas, which is primarily comprised of nitrogen and water vapor, is often conducted to an incinerator where it is burned before being discharged to the atmosphere. After any optional steam generation and/or heat exchange of the hot asphalt product stream, the asphalt product stream can be cooled prior to going to storage. Additionally or alternately, any vacuum gas oil that is desired for incorporation into the asphalt can be mixed with the oxidized vacuum resid after the oxidation process.
In various aspects, a variety of fractions suitable for incorporation into asphalt can be generated during processing of a heavy hydrocarbon feed. Examples of such fractions can include vacuum resid (566° C.+ vacuum resid), deep cut vacuum resid (˜580° C.+ vacuum resid), pentane rock, deasphalted oil, 427° C.-482° C. vacuum gas oil, 482° C.-538° C. vacuum gas oil, 510° C.-566° C. vacuum gas oil, and 538° C.-593° C. vacuum gas oil plus vacuum resid, and combinations thereof. It is understood that one or more of the above fractions, such as a plurality of the above fractions, can be used as asphalt components. It is further understood that blending of one or more of such asphalt components, such as a plurality of such asphalt components, can allow for formation of asphalt products with differing properties, depending in part on the proportions used of each asphalt component.
In the configuration shown in
Similar to the configuration shown in
It is noted that adding first portion 291 of the heavy hydrocarbon feed directly into blend 295 results in addition of some compounds boiling above the vacuum gas oil range to blend 295. This increases the net amount of 566° C.+ boiling compounds in blend 295. As a result, the amount of transport diluent included in blend 295 can range from 1.0 wt % to 20 wt %, or 1.0 wt % to 10 wt %. If desired, additional transport diluent 276 can be added to blend 295. In various aspects, before and/or after addition of transport diluent, the blended product can include a kinematic viscosity at 7.5° C. of 350 cSt or less and an API gravity of 19° or more, such as an API gravity of 19° to 20°.
An additional consideration for the configuration shown in
As still another variation, the vacuum separation stage 130 can be optional, so that the atmospheric bottoms 125 are passed into solvent deasphalter 370. In yet another variation, the atmospheric separation stage 120 and vacuum separation stage 130 can be optional, so that the input flow to the solvent deasphalter 370 corresponds to heavy hydrocarbon feed or an initial feed without separation of extraction site solvent.
The deasphalted oil 374 from solvent deasphalter 370 becomes one of the components incorporated into blend 395. Optionally, the deasphalted oil 374 can be hydrotreated (not shown) prior to incorporating the deasphalted oil into blend 395. In some aspects, at least some diluent can be included in blend 395. As a result, the amount of diluent included in blend 395 can range from 1.0 wt % to 20 wt %, or 1.0 wt % to 10 wt %. In other aspects, blend 395 can be formed without any additional diluent. In various aspects, either before or after removal/addition of transport diluent, the blended product can include a kinematic viscosity at 7.5° C. of 360 cSt or less, or 350 cSt or less, and an API gravity of 18° or more, or 19° or more.
In various aspects, the portion of the pitch that is not recycled back to the slurry hydroprocessing reactor (or other hydroconversion reactor) can be passed into a partial oxidation reactor. A partial oxidation reactor can be used to convert the slurry hydroprocessing pitch into hydrogen, carbon monoxide, and ash which can then be pelletized. The hydrogen generated during partial oxidation can be used as at least part of the hydrogen delivered to the slurry hydroprocessing reactor and/or the stabilizing hydrotreater. The pelletized ash thus corresponds to the other carbon-containing product that requires transport away from the extraction site.
In some aspects, the portion of the pitch used as the input flow to a partial oxidation reactor can have an ash content of 1.0 wt % or more, or 2.0 wt % or more, or 10 wt % or more, or 20 wt % or more, such as up to 40 wt %.
A vacuum resid fraction was hydroprocessed in a fixed bed reactor to determine the impact of recycle on reactor productivity.
As shown in
A pilot scale configuration similar to the configuration in
The heavy hydrocarbon feedstock was a 975° F.+(524° C.+) vacuum residue. The heavy hydrocarbon feedstock included more than 75 wt % of 566° C.+ components. The pilot plant included a pump-around loop that was operated with sufficient recirculation to reduce or minimize foaming. In the first reaction condition, a recycle stream was used that corresponded to 10 wt % of the fresh feed amount. In the second reaction condition, a recycle stream was used that corresponded to 50 wt % of the fresh feed amount. In the third reaction condition, the recycle stream corresponded to 100 wt % of the fresh feed amount (i.e., the mass flow rate of the recycle stream was substantially the same as the mass flow rate of the fresh feed). Table 1 provides additional details for each reaction condition, including the fresh feed rate that was needed to maintain conversion at roughly 90 wt % relative to 1050° F. (566° C.) based on the selected reaction temperature, pressure, and H2 treat gas rate. Table 1 also provides the relative reactor productivity for each condition, as well as a 566° C.+ conversion rate constant.
As shown in Table 1, Condition 1 corresponded to a conventional recycle, where a small recycle stream (˜10% of the fresh feed mass flow rate) containing less than 50 wt % 566° C.+ components was used for recycle. It is believed that the reactor productivity for Condition 1 is similar to what the reactor productivity would be without recycle. Conditions 2 and 3 corresponded to pitch recycle as described herein, where the amount of the recycle was 50% or more of the mass flow rate of the fresh feed, and the recycle stream included greater than 60 wt % 566° C.+ components. As shown in Table 1, operating with a substantial pitch recycle in Conditions 2 and 3 allowed for an increase in the fresh feed flow rate from 0.26 hr−1 (for 10% recycle) to either 0.36 hr−1 (for 50% recycle) or 0.41 hr−1 (for 100% recycle) while maintaining substantially constant conversion within the slurry hydroprocessing reactor. Thus, operating with substantial pitch recycle provided an unexpected productivity increase. This is in contrast to use of bottoms recycle when performing conversion in a fixed bed environment, where the bottoms recycle had substantially no impact on reactor productivity.
Table 2 shows the product yields from processing the heavy hydrocarbon feed at each condition. As shown in Table 2, even though Conditions 2 and 3 provided an unexpected productivity increase at constant conversion, the amount of hydrogen consumed unexpectedly decreased. This unexpected decrease appears to be due in part to reduced production of light ends and naphtha, with a corresponding increase in vacuum gas oil in the products. The reduction in light ends production also resulted in a net increase in liquid products (C5-566° C.) at Conditions 2 and 3. For the product fraction weight percentages in Table 2, the weight percentages are relative to the weight (i.e., mass flow rate) of the fresh feed.
It is noted that pitch recycle also improved the quality of the resulting vacuum gas oil (343° C.-566° C.), based on an increase in API gravity and a reduction in nitrogen content. Table 3 provides information similar to Table 2, but on a volume basis.
Embodiment 1. A method for upgrading a heavy hydrocarbon feed, comprising: separating a heavy hydrocarbon feed to form a first fraction comprising 50 wt % or more of a 566° C.+ portion, and one or more additional fractions comprising a 177° C.+ portion, the heavy hydrocarbon feed comprising an API gravity of 15° or less; exposing at least a portion of the first fraction and a pitch recycle stream to slurry hydroconversion conditions at a combined feed ratio of 1.5 or more to form a hydroconverted effluent, the hydroconversion conditions comprising a total conversion of 60 wt % to 89 wt % relative to 524° C.; separating at least a pitch recycle stream and a second hydroconverted fraction comprising a 177° C.+ portion from the hydroconverted effluent, the pitch recycle stream comprising more than 50 wt % of 566° C.+ components; and blending at least the one or more additional fractions and at least a portion of the second hydroconverted fraction to form a heavy hydrocarbon product having a kinematic viscosity at 7.5° C. of 500 cSt or less and an API gravity of 18° or more.
Embodiment 2. The method of Embodiment 1, wherein a vacuum gas oil fraction of the heavy hydrocarbon product comprises 0.5 wt % to 5.0 wt % of n-pentane insolubles, or wherein the heavy hydrocarbon product comprises 20 wt % or less of a 177° C.− fraction relative to a weight of the heavy hydrocarbon product, or a combination thereof.
Embodiment 3. The method of Embodiment 1, the method further comprising splitting an initial feedstock to form the heavy hydrocarbon feed and a second feedstock portion, the heavy hydrocarbon feed comprising 15 wt % to 95 wt % of the initial feedstock, wherein the blending comprises blending the second feedstock portion, the one or more additional fractions, and at least a portion of the second hydroconverted fraction to form a heavy hydrocarbon product, and optionally wherein a vacuum gas oil fraction of the heavy hydrocarbon product comprises 0.1 wt % to 2.0 wt % of n-pentane insolubles relative to a weight of the vacuum gas oil fraction
Embodiment 4. The method of Embodiment 3, wherein the initial feedstock further comprises a first diluent; wherein separating the heavy hydrocarbon feed comprises separating the heavy hydrocarbon feed to form the first fraction, a bypass fraction comprising a 566° C.+ portion, a diluent fraction comprising the first diluent, and the one or more additional fractions; and wherein the blending comprises blending the second feedstock portion, the bypass fraction, the one or more additional fractions, and at least a portion of the second hydroconverted fraction to form a heavy hydrocarbon product, the heavy hydrocarbon product optionally comprising 5 wt % to 15 wt % of the bypass fraction, relative to a weight of the heavy hydrocarbon product.
Embodiment 5. The method of any of the above embodiments, wherein the second hydroconverted fraction comprises an olefin-containing fraction, the method further comprising hydrotreating at least a portion of the olefin-containing fraction to form a hydrotreated product, and wherein blending at least the one or more additional fractions and at least a portion of the second fraction comprises blending at least the one or more additional fractions and at least a portion of the stabilized product to form the heavy hydrocarbon product.
Embodiment 6. The method of any of the above embodiments, wherein the pitch recycle stream comprises 60 wt % or more of 566° C.+ components, or wherein the pitch recycle stream comprises 50 wt % or more of 593° C.+ components, or a combination thereof.
Embodiment 7. The method of any of the above embodiments, wherein the first fraction comprises 60 wt % or more of 566° C.+ components, or wherein the first fraction comprises 50 wt % or more of 593° C.+ components, or a combination thereof.
Embodiment 8. The method of any of the above embodiments, wherein the combined feed ratio is 1.6 to 3.0, or wherein a weight of the first fraction is 50 wt % or less of a weight of the heavy hydrocarbon feed, or a combination thereof.
Embodiment 9. The method of any of the above embodiments, wherein the per-pass conversion at 524° C. is 50 wt % or less, or wherein the per-pass conversion at 524° C. is lower than the total conversion at 524° C. by 25 wt % or more, or a combination thereof.
Embodiment 10. The method of any of the above embodiments, wherein the one or more additional fractions comprise 5.0 wt % or less of 177° C.− components, or wherein the heavy hydrocarbon product comprises 10 wt % or less of the 177° C.− fraction, or a combination thereof.
Embodiment 11. The method of any of the above embodiments, wherein the heavy hydrocarbon product comprises 50 wt % or more of a 343° C.-566° C. fraction relative to a weight of the heavy hydrocarbon product; or wherein the first fraction comprises a first nitrogen content, and wherein the hydroconverted effluent comprises an effluent 177° C.+ portion, the effluent 177° C.+ portion comprising a nitrogen content that is at least 75 wt % of the first nitrogen content; or a combination thereof.
Embodiment 12. The method of any of the above embodiments, wherein separating the heavy hydrocarbon feed comprises performing solvent deasphalting on at least a portion of the heavy hydrocarbon feed, and wherein the first fraction comprises deasphalter rock.
Embodiment 13. The method of any of the above embodiments, wherein the slurry hydroconversion conditions comprise a temperature of 400° C. to 480° C., a pressure of 1000 psig (˜6.4 MPa-g) to 3400 psig (˜23.4 MPa-g), and a LHSV of 0.05 hr−1 to 5 hr−1.
Embodiment 14. The method of any of the above embodiments, wherein the blending comprises blending at least a diluent comprising a 177° C.− portion, the one or more additional fractions, and the at least a portion of the second hydroconverted fraction to form the heavy hydrocarbon product.
Embodiment 15. The method of any of the above embodiment, wherein separating the heavy hydrocarbon feed comprises: separating a feedstock comprising a first diluent and the heavy hydrocarbon feed to form the first fraction, the one or more additional fractions, and a diluent fraction comprising at least a portion of the first diluent, the first diluent comprising 177° C.− components.
Additional Embodiment A. The method of any of Embodiments 1, 2, or 5 to 15, wherein the heavy hydrocarbon product comprises 1.0 wt % or less of 621° C.+ components, or wherein the heavy hydrocarbon product comprises 5.0 wt % or less of 593° C.+ components, or a combination thereof, relative to a weight of the heavy hydrocarbon product.
Additional Embodiment B. The method of any of Embodiments 3 to 15, wherein the first feedstock portion comprises 15 wt % to 80 wt % of the initial feedstock, or 20 wt % to 95 wt %, or 30 wt % to 95 wt %, or 30 wt % to 80 wt %, or 30 wt % to 70 wt %, or 15 wt % to 50 wt %, or 50 wt % to 95 wt %, or 50 wt % to 80 wt %.
When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains.
The present invention has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/046273 | 8/14/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62896380 | Sep 2019 | US |
