Method of and means for upgrading hydrocarbons containing metals and asphaltenes

Abstract

A hydrocarbon source feed is upgraded using a solvent deasphalting (SDA) unit employing a solvent having a critical temperature Tc by initially separating from a first hydrocarbon input stream fractions with an atmospheric equivalent boiling temperature less than about Tf° F. for producing a stream of Tf−fractions and a residue stream (Tf+ stream), where Tf is greater than about Tc−50° F. In the SDA unit, a second hydrocarbon input stream which includes the residue stream is deasphalted for producing a first product stream of substantially solvent-free asphaltenes, and a second product stream containing substantially solvent-free deasphalted oil (DAO). The source feed may be included in either the first or second input streams. The DAO in the second product stream is thermally cracked for producing an output stream that includes thermally cracked fractions and by-product asphaltenes produced by thermally cracking the DAO. Finally, at least some the said thermally cracked fractions are included in the first input stream.

Description

TECHNICAL FIELD

This invention relates to upgrading of hydrocarbons containing metals and asphaltenes and more particularly is concerned with a method of and means for upgrading such hydrocarbons prior to their use as fuel in power generation systems or as refinery feedstocks.

BACKGROUND TO THE INVENTION

Many liquid hydrocarbons are comprised of various fractions which- vaporize under atmospheric or subatmospheric pressure, at different temperatures. In typical practice, such hydrocarbons are fractionated by heating and vaporizing one or more of such fractions to separate the lighter, lower boiling range fractions from the heavier, higher boiling range material. Since the process of fractionation separates the lighter, lower boiling range fractions as vapors, certain constituents of the hydrocarbons which do not vaporize remain in the heavier, higher boiling range portion of the hydrocarbon. Examples of constituents with this characteristic include metals, asphaltenes (pentane-insolubles), and coke pre-cursors, such as those measured by ASTM test procedures D-189 and designated as Conradson Carbon Residue (CCR).

These constituents are a problem for a variety of potential users of the heavier, higher boiling range portion of the hydrocarbon. Examples of users for whom such constituents present a problem include power generation devices, such as combustion turbines and internal combustion engines, and refinery process units such as catalyst-based cracking and hydrotreating units and thermal cracking units.

An example of a user that is effected by the constituents present in the heavier, higher boiling range portion of oil is the combustion turbine, which is one of the lowest cost, highest efficiency power generation systems available today. Combustion turbines can also be configured in a combined cycle configuration to further increase the efficiency of a power generation cycle. Combustion turbines can be damaged when using liquid fuels that contain significant amounts of metals. To avoid such damage, users of combustion turbines can: (1) use fuel with low levels of metals, (2) use fuel pre-processing systems to reduce the level of metals in the fuel burned, (3) add chemicals to the fuel to reduce the negative impacts of the metals in the fuel, or (4) operate the combustion turbine at a lower, and less efficient firing temperature to reduce the impact of the metals. Each of these options results in an increased cost of power generation, whether from additional capital, additional operating costs, or lower power generation efficiency.

One of the lowest cost liquid fuels available for use in combustion turbines is heavy fuel oil. Such oil is produced by mixing the heavier, higher boiling range portion of the hydrocarbon with sufficient light petroleum diluent, e.g., diesel fuel, to achieve the desired product properties. While the resultant heavy fuel oil usually has a lower cost than other liquid fuel products, the level of metals in the oil is usually higher, causing higher operating and maintenance costs and lower power generation efficiencies in combustion turbines. Moreover, such heavy fuel oil contains some amount of light petroleum product as diluent and the diluent alone has a higher value than that of the heavy fuel oil.

Conventionally, the low quality of the heavy fuel oil can be improved prior to use by fuel treatment systems such as centrifuging or settling to remove sediment, water washing to remove water soluble corrosive salts, and the addition of inhibitors to control the effect of non-removable corrosive elements.

The cost of heavy fuel oil can be reduced by purchasing a lower quality product, which then requires the use of a greater amount of fuel treatment, which results in lower combustion turbine efficiency and increases downtime.

In U.S. Pat. No. 4,191,636, heavy oil is continuously converted into asphaltenes and metal-free oil by hydrotreating the heavy oil to crack asphaltenes selectively and remove heavy metals such as nickel and vanadium simultaneously. The liquid products are separated into a light fraction of an asphaltene-free and metal-free oil and a heavy fraction of an asphaltene and heavy metal-containing oil. The light fraction is recovered as a product and the heavy fraction is recycled to the hydrotreating step.

In U.S. Pat. No. 4,528,100, a process for the treatment of residual oil is disclosed, the process comprising the steps of treating the residual oil so as to produce a first extract and a first raffinate using supercritical solvent extraction, and then treating the first raffinate so as to produce a second extract and a second raffinate again by supercritical solvent extraction using a second supercritical solvent and then combining the first extract and the raffinate to a product fuel. In accordance with a particular embodiment of the invention disclosed in the U.S. Pat. No. 4,528,100, the supercritical solvents are particularly selected to concentrate vanadium in the second extract. Thus, even though the amount of vanadium present in the product fuel is low and consequently beneficial for reducing gas turbine maintenance problems as stated in this U.S. Pat. No. 4,528,100, some amount of vanadium does still remain therein.

Another example of a user of the heavier, higher boiling range portion of a hydrocarbon is a refinery with a fluid catalytic cracking unit (an FCC unit). FCC units typically are operated with a feedstock quality constraint of very low metals asphaltenes, and CCR (i.e., less than 10 wppm metals, less than 0.2 wt % asphaltenes, and less than 2 wt % CCR). Utilization of feedstocks with greater levels of asphaltenes or CCR results in increased coke production and a corresponding reduction in unit capacity. In addition, use of feedstocks with high levels of metals and asphaltenes results in more rapid deactivation of the catalyst, and thus increased catalyst consumption rates and increased catalyst replacement costs.

In U.S. Pat. No. 5,192,421, a process for the treatment of whole crude oil is disclosed, the process comprising the steps of deasphalting the crude by first mixing the crude with an aromatic solvent, and then mixing the crude-aromatic solvent mixture with an aliphatic solvent. The U.S. Pat. No. 5,192,421, (at page 9, lines 43-45) identifies that certain modifications must be made to prior art solvent deasphalting technologies, such as that described in U.S. Pat. Nos. 2,940,920, 3,005,769, and 3,053,751 in order to accommodate the process described in the U.S. Pat. No. 5,192,421, in particular since the prior art solvent deasphalting technologies have no means to remove that portion of the charge oil that will vaporize concurrently with the solvent and thus contaminate the solvent used in the process. In addition to being burdened by the complexity and cost resulting from the use of two solvents, the U.S. Pat. No. 5,192,421 process results in a deasphalted product that still contains a non-distilled portion with levels of CCR and metals that exceed the desired levels of such contaminants.

In U.S. Pat. No. 4,686,028 a process for the treatment of whole crude oil is disclosed, the process comprising the steps of deasphalting a high boiling range hydrocarbon in a two-stage deasphalting process to produce separate asphaltene, resin, and deasphalted oil fractions, followed by upgrading only the resin fraction by hydrogenation or visbreaking. The U.S. Pat. No. 4,686,028 is burdened by the complexity and cost of a two-stage solvent deasphalting system to separate the resin fraction from the deasphalted oil, in addition, like the U.S. Pat. No. 5,192,421, the U.S. Pat. No. 4,686,028 process results in an upgraded product that still contains a non-distilled fraction—the DAO—that is contaminated with CCR and metals.

In U.S. Pat. No. 4,454,023 a process for the treatment of heavy viscous hydrocarbon oil is disclosed, the process comprising the steps of visbreaking the oil; fractionating the visbroken oil; solvent deasphalting the non-distilled portion of the visbroken oil in a two-stage deasphalting process to produce separate asphaltene, resin, and deasphalted oil fractions; mixing the deasphalted oil with the visbroken distillates; and recycling and combining resins from the deasphalting step with the feed initially delivered to the visbreaker. The U.S. '023 patent is burdened by the complexity and cost of a two-stage solvent deasphalting system to separate the resin fraction from the deasphalted oil. In addition, the '023 process results in an upgraded product that still contains a non-distilled fraction—the DAO—that is contaminated with CCR and metals.

In U.S. Pat. No. 5,601,697 a process is disclosed for the treatment of topped crude oil, the process comprising the steps of vacuum distilling the topped crude oil, deasphalting the bottoms product from the distillation, catalytic cracking of the deasphalting oil, mixing the distillable catalytic cracking fractions (atmospheric equivalent boiling temperature of less than about 1100° F.) to produce products comprising transportation fuels, light gases, and slurry oil. The U.S. Pat. No. '697 is burdened by the complexity, cost, and technical viability of vacuum distilling a topped heavy crude to about 850° F. and catalytic cracking the deasphalted oil to produce transportation fuels. This level of upgrading is too complex and required too large of a scale to be useful for oil field applications, and U.S. Pat. No. '697 selectively eliminates the majority of the material that could be used as fuel for a combustion turbine or internal combustion engine without further upgrading.

It is therefore an object of the present invention to provide a new and improved method of and means for upgrading hydrocarbons containing metals and asphaltenes wherein the disadvantages as outlined are reduced or substantially overcome.

SUMMARY OF THE INVENTION

According to the present invention, a method of and means for upgrading a hydrocarbon containing metals and asphaltenes is provided, the method comprising the steps of: supplying the hydrocarbon containing metals and asphaltenes to a vaporizer present in a deasphalting unit and operating at, above, or below atmospheric pressure for heating and vaporizing the hydrocarbon at a temperature sufficient to vaporize at least that fraction of the hydrocarbon which has an atmospheric boiling temperature less than about 50° F. below the critical temperature of the solvent used in the deasphalting unit; removing and subsequently condensing the hydrocarbon fraction so vaporized from the balance of the hydrocarbon to be upgraded, prior to the addition of the solvent to the hydrocarbon; and processing the hydrocarbon remaining after the initial vaporization step in a solvent deasphalting unit such as that disclosed in copending U.S. patent application Ser. No. 08/862,437 filed on May 23, 1997, the disclosure of which is hereby included by reference, to produce atmospheric distillate, deasphalted oil (DAO) and asphaltenes.

Usually, the step of supplying the hydrocarbon to a vaporizer present in a deasphalting unit and operating at, above, or below atmospheric pressure for heating and vaporizing the hydrocarbon is carried out by supplying the hydrocarbon to a heater for heating the hydrocarbon and thereafter supplying the heated hydrocarbon to a fractionation column. If a prior art solvent deasphalting unit is used, all of the material boiling below an atmospheric equivalent temperature of about 450° F. will have to be removed in the vaporization step in order to prevent contamination of the solvent, and the SDA unit will produce only DAO and asphaltenes. In a preferred embodiment of the present invention, the DAO (or atmospheric DAO) is firstly fractionated in a fractionation column which may be a distillation column or flash vessel which may be included in the SDA unit to produce vacuum distillate (i.e., fractions with atmospheric equivalent boiling temperatures less than about 1100° F.) and non-distilled DAO residue (vacuum DAO), and the non-distilled DAO residue is heated for sufficient time and at suitable temperature conditions to thermally crack the non-distilled DAO residue into thermally cracked lighter, lower boiling range fractions (comprising thermally cracked fractions with atmospheric equivalent boiling temperatures less than about 1100° F.), and a thermal cracker residue fraction (thermal cracker residue, or TCR, comprising by-product asphaltenes, unconverted vacuum DAO, thermal cracker gases, etc.); and fractionating the TCR in a further fractionation column operating at sub-atmospheric pressure to separate thermally cracked vacuum distillate fractions (i.e., fractions with atmospheric equivalent boiling temperatures in the range 650-1050° F.) from the non-distilled TCR. Note that throughout the text the term fractionating, column is used and is taken to mean a distillation column or flash vessel.

The distilled, thermally cracked and low boiling range fractions and the thermally cracked vacuum distillate are substantially asphaltene-free and metal-free and can be used, alone or re-combined with one or more of the distillate fractions obtained from the original feedstock, without further treatment, as a replacement for premium distillate fuels or refinery feedstocks.

According to the present invention, the TCR fraction can be substantially recycled and combined with the feed to the solvent deasphalting unit.

In the course of cracking the non-distilled DAO residue, asphaltenes are produced as a by-product of the thermal cracking process. Under severe thermal cracking conditions, such as would be employed to maximize the generation of lighter products, sufficient asphaltenes can be created in the thermal cracking step so as to cause precipitation of asphaltenes and fouling of the thermal cracker heater exchanger, or precipitation of the asphaltenes from the thermal cracker in subsequent storage or transport. The precipitation of asphaltenes thus produces a limit on the severity and yield of lighter, lower boiling range fractions and vacuum distillate fractions from the thermal cracking process.

According to the present invention, the asphaltenes present in the hydrocarbons to be upgraded are removed in the deasphalting step prior to the thermal cracking step. In addition, by recycling the TCR, which contains asphaltenes created as a by-product of the thermal cracking to the solvent deasphalting step, the thermal cracker-produced asphaltenes are removed from the TCR and the deasphalted TCR can be returned to the thermal cracker for further cracking. Thus, according to the present invention, the removal of asphaltenes from the initial and the recycled feedstocks to the thermal cracker allow for a much improved level of conversion of non-distilled hydrocarbon into distillates than is possible with the prior art.

Furthermore, in accordance with the present invention, the recycled TCR stream can be used to provide at least some of the heat required to achieve the desired temperature for the initial vaporization step of the process.

According to the present invention, the asphaltenes produced from the invention can be used as fuel by another fuel user. For example, these asphaltenes can be used as fuel in a fluidized bed combustor or high viscosity fuel oil boiler, or emulsified and used in as an alternative to heavy fuel oil in conventional systems. Alternatively, the asphaltenes can be used As fuel in a gasifier, or they can be cracked to produce lighter liquid fuels. If so cracked, the distillate fuel produced from the asphaltenes can be combined with the distillate products that result from the cracking of the DAO or from the fractionation of the original feedstock to the process.

In accordance with another embodiment of the present invention, the hydrocarbon to be upgraded can sometimes comprise non-distilled residue which contains metals, asphaltenes, and CCR, combined with a lower-boiling range hydrocarbon diluent to achieve a desired viscosity and density of the combined oil. Such diluent, if separated from the non-distilled residue, is a valuable fuel which requires no further processing. In the case of a non-distilled-heavy oil and diluent mixture, the invention would comprise of the steps of supplying the heavy oil or hydrocarbon mixture to a diluent vaporizer present in the deasphalting unit for heating and vaporizing the hydrocarbon at a temperature sufficient to vaporize or boil off the diluent and subsequently condensing the diluent; and processing the remaining distillation residue in the deasphalting unit as previously described. Usually the step of supplying the heavy oil or hydrocarbon mixture to a vaporizer present in a deasphalting unit for heating and vaporizing the diluent is carried out by supplying the heavy oil or hydrocarbon mixture to a heater for heating the heavy oil or hydrocarbon mixture and thereafter supplying the heated heavy oil or hydrocarbon mixture to a fractionation column.

In accordance with another embodiment of the invention, if the hydrocarbons to be upgraded contains a fraction that is distillable at an equivalent atmospheric boiling temperature less than about 50° F. below the critical temperature of the solvent used in the solvent deasphalting step, the invention can be used to simultaneously fractionate and deasphalt in one device to produce as separate products distillates, non-distillable deasphalted oil, and asphaltenes.

In a further embodiment of the invention, diluent, either from a deasphalting unit or from another source, can be added to the asphaltenes exiting the deasphalting unit to produce heavy fuel oil.

In another embodiment of the invention, if the invention is used at the site of a power generation system, such as a combustion turbine, to produce fuel for the power generation, system, then waste heat from the power generation unit can be used to provide at least some of the thermal energy required by the deasphalting or thermal cracking steps.

Furthermore, the present invention also comprises means or apparatus for carrying out the method or methods of the present invention. In an embodiment of means for upgrading hydrocarbons containing metals and asphaltenes in accordance with the present invention, apparatus comprises a heat exchanger and vaporizer contained in a deasphalting unit for heating the hydrocarbons to a temperature sufficient to vaporize at least that fraction of hydrocarbon which has an atmospheric boiling temperature less than about 50° F. below the critical temperature of the solvent used in the solvent deasphalting process and boiling off and subsequently condensing the fraction so vaporized; and means for supplying the remaining hydrocarbon to a deasphalting unit such as that disclosed in copending U.S. patent application Ser. No. 08/862,437 filed on May 23, 1997, for producing deasphalted oil (DAO) and asphaltenes. If a prior art solvent deasphalting unit is used, all of the material boiling below an atmospheric equivalent temperature of about 450-650° F. will have to be removed in the vaporization step in order to prevent contamination of the solvent, and the SDA unit will produce only DAO and asphaltenes. In a preferred embodiment of the present invention, means for fractionating the resulting deasphalted oil under sub-atmospheric conditions are provided which may be included in the SDA unit, as well as means for thermally cracking and distilling the non-distillate residue of the DAO.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described by way of example, and with reference to the accompanying drawings wherein:

FIG. 1A is a block diagram of one embodiment of a heavy oil upgrader according to the present invention;

FIG. 1B is a block diagram of a modified version of the embodiment of FIG. 1A ;

FIG. 2A is a block diagram showing details of the front-end and solvent deasphalting unit of a heavy oil upgrader according to the present invention;

FIG. 2B is a block diagram showing details of a further portion of the upgrader shown in FIG. 2A ;

FIG. 3 is a block diagram showing details of a thermal cracker and other components of the upgrader shown in FIGS. 2A and 2B ;

FIG. 4A is a block diagram of one embodiment of a power plant incorporated into an upgrader according to the present invention;

FIG. 4B is a block diagram of a modified version of the embodiment of FIG. 4A ;

FIG. 5 is a block diagram of a further embodiment of a power plant incorporated into an upgrader according to the present invention;

FIG. 6 is a block diagram of a still further embodiment of the present invention; and

FIG. 7 is a schematic showing of the use of waste heat in a conventional power generation system for supplying heat to an upgrader according to the present invention.

DETAILED DESCRIPTION

Turning now to the drawings wherein like reference characters in the various figures designate like components, reference numeral 10 A in FIG. 1A , and reference numeral 10 B in FIG. 1B , designate embodiments of a heavy oil upgrader according to the present invention. Upgrader 10 A functions to upgrade a source feed of crude oil, which is mainly heavy hydrocarbons but typically contains light fractions, heavy metals, asphaltenes, etc., to a plurality of valuable non-asphaltene product streams including atmospheric and vacuum distillates, etc., and to a less valuable asphaltene product stream that contains most of the metals, coke pre-cusors, etc. present in the source feed. Upgrader 10 B in FIG. 1B functions to upgrade a source feed, such as atmospheric or vacuum residual, which lacks light fractions with atmospheric equivalent boiling temperatures below about 450° F.

An upgrader according to the present invention, utilizes a solvent deasphalting (SDA) unit 11 that employs a solvent having a critical temperature T c , and includes fractionator 12 constructed as a distillation column, and arranged to separate from first hydrocarbon input stream 13 , fractions with an atmospheric equivalent boiling temperature less than about T f °F. for producing stream 14 of T f − fractions (e.g., naphtha, atmospheric distillate, vacuum distillate, etc.) and residue stream 15 (T f + stream), where T f is greater than about T c −50° F. Typically, T f will be less than about 1100° F.

SDA unit 11 , which may be either of conventional design, or constructed in accordance with the details shown in FIGS. 2A , 2 B, and 3 , deasphalts second hydrocarbon input stream 16 , which includes residue stream 15 , for producing first product stream 17 of substantially solvent-free asphaltenes, and second product stream 18 containing substantially solvent-free deasphalted oil (DAO).

Source feed 19 A is included in first input stream 13 ( FIG. 1A ) when feed 19 A contains fractions with an atmospheric equivalent boiling temperature less than about T f °F. However, if source feed 19 B contains no such fractions, then source feed 19 B bypasses fractionator 12 and is included in the second input stream (FIG. 1 B). Thus, the source feed is included in either the first or second input streams according to the nature of the source feed.

Second product stream 18 containing DAO is heated in heater 20 and then cracked in thermal cracker 21 . The cracking operation that takes place in cracker 21 produces output stream 22 that includes thermally cracked fractions and by-product asphaltenes produced by thermally cracking the DAO. Stream 22 also contains unconverted DAO the level of which is dependent on the efficiency of conversion of thermal cracker 21 .

At least some of the thermally cracked fractions in stream 22 are fed back through heat exchanger 23 to first input stream 13 supplying fractionator 12 . The entire output stream may be fed back to allow fractionator 12 to separate all of the lighter fractions produced by the thermal cracking process, and to allow the SDA unit to separate by-product asphaltenes produced by the thermal cracking process.

Stream 14 of T f − fractions produced by fractionator 12 is cooled prior to storage or use by passing this stream through heat exchanger 24 wherein heat contained in stream 14 is transferred to the source feed which is preheated in preparation either for removing light fractions (FIG. 1 A), or for processing by SDA unit 11 (FIG. 1 B). Note that in FIG. 1A , the first input stream consists of source feed 19 A and output 22 of the thermal cracker, and the second input stream consists of residue stream 15 . In FIG. 1B , the first input stream consists of output 22 of the thermal cracker, and the second input stream consists of source feed 19 B and residue stream 15 .

The upgraders shown in FIGS. 1A and 1B have a single input, namely, a hydrocarbon source feed, and two main products as outputs: a range of non-asphaltene product streams of valuable light fractions, and a less valuable asphaltene product stream. Thus, the upgraders of the present invention represent a particularly simple technological solution for upgrading heavy hydrocarbon feedstock to provide fuel for power generation, or feedstock for a refinery.

Preferably, the fractionator shown in FIG. 1 A and FIG. 1B is integrated into an SDA unit to establish a new and improved upgrader designated by reference numeral 30 in FIGS. 2A , 2 B and 3 . Referring first to FIG. 2A , upgrader 30 receives hydrocarbon feed 31 , such as crude oil usually containing light fractions, which if not removed upstream of SDA unit 18 ′, adversely affect the operation of the SDA unit due to the trapping of the light fractions in the solvent. The feed is heated in passing through serially disposed heat exchangers E 1 and E 2 (which correspond to heat exchanger 24 in FIG. 1 A), and H 1 to about 450° F. and applied to fractionator V 1 which produces a stream of atmospheric distillate (i.e., fractions such as naphtha with atmospheric equivalent boiling temperatures less that about 450° F.) which passes out the top of the fractionator. The stream of atmospheric distillate flows through conduit 33 and is cooled by transferring heat to feed 31 in heat exchanger E 2 forming a product stream in conduit 33 ′. Residue 32 passes out the bottom of fractionator V 1 . Because this residue is what remains in the fractionator after atmospheric distillate is removed, thus residue is referred to as atmospheric residue for reference purposes.

In order to utilize a solvent deasphalting process to separate asphaltenes in residue 32 , the temperature of the residue must be reduced from that of the fractionator V 1 to about T c where T c is the critical temperature of he solvent prior to mixing the residue with a solvent. To this end, the residue is pumped through conduit 34 by pump P 1 at the outlet 34 ′ of fractionator V 1 , to inlet 34 ″ of mixer M 1 after passing through serially disposed heat exchangers E 3 , E 4 and E 5 . If feed 31 is vacuum resid, heat exchangers H 1 , E 3 , E 4 , and E 5 would be by-passed, and the feed exiting heat exchanger E 2 would be applied directly to input 34 ″ of mixer M 1 as indicated by chain line 40 .

Mixer M 1 mixes the cooled residue from fractionator V 1 with a solvent (e.g., liquid pentane), and the mixture is applied to asphaltene separator V 2 wherein gravity separates the mixture into lighter deasphalted oil (DAO) and heavier asphaltenes. Through conduit 35 at the top of the separator flows a mixture stream of DAO and solvent, and through conduit 36 at the bottom flows a mixture stream of asphaltenes and solvent in which a small amount of DAO is dissolved.

A product stream of substantially solvent-free DAO (termed atmospheric DAO product stream because atmospheric distillate has been removed upstream of SDA unit 18 ′) is produced by SDA 18 ′ by sequentially applying the mixture of DAO and solvent in conduit 35 , first to supercritical solvent recovery section 37 , and then to evaporative solvent recovery section 38 . A product stream of substantially solvent-free asphaltene is also produced by SDA 18 by applying the asphaltene and solvent mixture, directly to evaporative solvent recovery section 38 .

Section 37 includes serially disposed heat exchangers E 6 - 9 associated with conduit 35 so that the stream of DAO and solvent produced by separator V 2 is heated to above the critical temperature of the solvent before reaching DAO separator V 3 of section 37 . In this separator, phase separation of the fluid takes place producing a stream of solvent that flows out the top of separator V 3 into conduit 39 , and a mixture of DAO and reduced solvent that flows out the bottom of the separator into conduit 40 .

The temperature of the stream of solvent leaving separator V 3 is above the critical temperature of the solvent and must be cooled before it can be recycled to mixer M 1 . Preferably, the stream of hot solvent is cooled by passing it through heat exchanger E 6 and cooler E 10 in preparation for recovering and then recycling the solvent to mixer M 1 . Thus, some of the heat added to the stream of DAO and solvent in conduit 35 to raise the temperature of the stream to above the critical temperature of the solvent is recovered in heat exchanger E 6 by cooling the hot solvent from separator V 3 . Further cooling of the solvent to the desired temperature for use in mixer M 1 is effected by condenser E 10 whose operation is controlled to achieve the desired final temperature at the outlet of pump P 2 which supplies solvent to mixer M 1 .

The temperature of the stream of DAO and reduced solvent leaving separator V 3 through conduit 40 at the bottom of the separator is also above the critical temperature and pressure of the solvent. In preparation for flashing this stream in flash drum V 5 in evaporative section 38 , which evaporates the reduced solvent and produces a substantially solvent-free product steam of atmospheric DAO, the stream of DAO and reduced solvent is further heated in heat exchanger E 3 by transferring heat from the residue flowing from fractionator V 1 . Thus, some of the heat added to the stream in conduit 31 by heater H 1 is recovered by heat exchanger E 3 .

In a similar manner, the stream of asphaltene and solvent mixture in conduit 36 produced by separator V 2 , which is cooler than the DAO and reduced solvent stream in conduit 40 produced by separator V 3 , is heated in preparation for flashing this stream in flash drum V 4 of evaporation section 38 . First, the stream in conduit 36 passes through heat exchanger E 4 downstream of heat exchanger E 3 extracting heat from residue 32 produced by fractionator V 1 . The thus preheated stream is further heated in heat exchanger E 11 supplied with hot fluid (preferably hot DAO product from hot oil supply HOS, FIG. 2 B).

In parallel operations in section 38 , the stream of DAO and reduced solvent leaving heat exchanger E 3 is flashed in drum V 5 , and the stream of asphaltene and solvent leaving heat exchanger E 11 is flashed in drum V 4 producing vaporized solvent that is applied to heat exchanger E 7 wherein the DAO and solvent stream in conduit 35 is heated. The residues produced by the flash drums are respectively applied to strippers V 6 and V 7 wherein, with the aid of injected steam and reduced pressure, a substantially solvent-free product stream of atmospheric DAO is produced at the bottom of stripper V 7 , and a substantially solvent-free product stream of asphaltene is produced at the bottom of stripper V 6 .

Before describing the further processing of these two product steams, the disposition of the vaporized solvent produced by flash drums V 4 and V 5 , and of the mixture of vaporized solvent and steam produced by strippers V 6 and V 7 is described. After the vaporized solvent produced by drums V 4 and V 5 is cooled somewhat in heat exchanger E 7 , the solvent may still be too hot for proper expansion in an organic turbine. As a consequence, the solvent is further cooled in heat exchanger E 12 (which preheats solvent pumped by pump P 3 , P 4 from solvent storage tank V 10 ); and the cooler vaporized solvent is applied to separator V 8 for the purpose of separating any atmospheric distillate trapped in the solvent.

Vaporized solvent exits from the top of separator V 8 and is applied to the inlet stage of organic vapor turbine T wherein expansion occurs driving generator G and producing power. Heat depleted solvent at lower pressure is exhausted from this turbine, cooled in heat exchanger E 13 (which preheats solvent pumped by pump P 3 , P 4 from solvent storage tank V 10 ) to remove some of the superheat from the heat-depleted turbine exhaust, and then condensed in air-cooled condenser E 14 producing liquid solvent that is stored in tank V 10 .

The fluid that exits from the bottom of separator V 8 comprises atmospheric distillate and a residual amount of solvent. To this fluid is added the solvent and steam from the overhead of strippers V 6 and V 7 ; and the combined fluid, a mixture of atmospheric distillate, solvent, and steam flows though heat exchanger 15 to separator V 9 . Cooling of the fluids in heat exchanger E 15 causes the steam and atmospheric distillate to condense in separator V 9 . The lower layer of liquid in the separator is water which is drained from the bottom, and the upper layer is a liquid comprising atmospheric distillate and perhaps some naphtha and condensed solvent, which flows to point W upstream of separator V 14 . Most of the solvent in separator V 9 remains vaporized and is delivered to solvent condenser E 14 .

As indicated above, pumps P 3 , P 4 also deliver make-up solvent to mixer M 1 via pump P 2 . Condenser E 10 is operated at a level that will establish the appropriate temperature for the solvent applied by pump P 2 to mixer M 1 taking into account the temperature of the solvent in tank V 10 , and the temperature of the solvent exiting heat exchanger E 6 . In addition to supplying make-up solvent to mixer M 1 , pumps P 3 , P 4 also supply solvent from tank V 10 to an intermediate stage of turbine T along three parallel paths. In one path, the solvent is heated by passing through heat exchangers E 13 and E 12 . In a second path, solvent is heated by passing through heat exchanger E 13 and heat exchanger E 19 whose function is to cool atmospheric distillate produced downstream of the SDA unit by a thermal cracking operation described below. In a third path, the solvent is heated by passing through heat exchangers E 13 and E 15 . Thus, the turbine will generate additional power using heat extracted from the solvent in the turbine exhaust prior to condensation, from the solvent produced by flash drums V 4 and V 5 , strippers V 6 and V 7 , and from atmospheric distillate produced by the SDA unit and the thermal cracker that is downstream of the SDA unit.

The mixture of liquids at point W arriving from separator V 9 is joined by the distillate that passes through heat exchanger E 2 , and distillate (produced by the downstream thermal cracking operation) that passes through heat exchanger E 1 . This combined stream is applied to separator V 14 wherein, at a reduced pressure, the lighter fractions vaporize and pass out the top of the separator. The vapor passing out the top of separator V 14 is vaporized solvent, steam, and naphtha. This vapor is cooled in condenser E 18 and supplied to separator V 15 in which the water and naphtha separate from the solvent which remains a vapor and is returned by pump P 12 to solvent condenser E 14 . The naphtha and steam are separated from each other in separator V 16 , the water being drawn from the bottom of this separator. The naphtha is pumped at P 10 to point Z where it is combined with liquid atmospheric distillate from the bottom of separator 14 , and with vacuum distillate produced by the thermal cracker downstream of SDA unit 18 ′ to produce a finished product stream that is supplied to tankage or pipeline.

As described above, the apparatus shown in FIG. 2A receives a hydrocarbon feed at 31 , and produces the following: a product stream of substantially solvent-free atmospheric DAO at the output of stripper V 7 , a product stream of substantially solvent-free asphaltene at the output of stripper V 6 ; and, at point Z, a product stream that is a blend of virgin atmospheric and vacuum distillates and naphtha (i.e., fractions present in the original feed), as well as atmospheric and vacuum distillates and naphtha produced by the thermal cracking process applied to the DAO product stream.

Pump P 6 at the outlet of stripper V 7 delivers the atmospheric DAO product stream to holding tank V 12 as shown in FIG. 2B to which reference is now made. Tank V 12 is at ambient temperature, and any solvent or light noncondensable gases in the DAO are removed from the overhead of this tank and burned with additional fuel to heat DAO from tank V 12 delivered by pump P 7 to heater H 2 . Some of the hot DAO produced by heater H 2 is supplied to heat exchanger E 9 in supercritical section 37 of the SDA unit ( FIG. 2A ) and to heater H 1 upstream of fractionator V 1 (FIG. 2 A). Because the hot DAO used as a heat exchange fluid is constantly renewed by the SDA unit, the quality of the heat exchange fluid supplied to the SDA unit for heating does not deteriorate over time. This technique is disclosed in copending application Ser. No. 08/710,545 filed Sep. 19, 1996, the disclosure of which is hereby incorporated by reference.

The bulk of the hot DAO, however, is supplied to vacuum fractionator V 13 which produces at its overhead, a stream of fractions with atmospheric equivalent boiling temperatures less than about 1100° F. (vacuum distillate), and which at its bottom, produces a residue stream that is termed vacuum DAO (i.e., DAO that remains after vacuum distillate is removed). The vacuum distillate produced by fractionator V 13 is cooled in heat exchanger E 8 ( FIG. 2A ) which helps raise the DAO and solvent mixture from the asphaltene separator to the supercritical temperature of the solvent, and then further cooled in heat exchanger E 1 ( FIG. 2A ) which helps raise the temperature of feed 31 upstream of fractionator V 1 .

The product stream of vacuum DAO is supplied by pump P 13 to heat exchanger E 22 ( FIG. 3 ) wherein the stream is preheated, and then to heater H 3 wherein the temperature of the stream is raised to about 900° F. From this heater, the hot DAO flows to holding tank V 17 of a size that provides sufficient residence time for thermal cracking of the DAO to take place. The thermally cracked stream produced by thermal cracker V 17 comprises fractions with atmospheric equivalent boiling temperatures ranging through about 1100° F., by-product asphaltenes produced by the thermal cracking process, unconverted vacuum DAO, thermal cracker gas, etc. all at about 900° F. This hot thermally cracked stream is cooled by passing through heat exchanger E 22 which serves to heat the stream of vacuum DAO from fractionator V 13 ( FIG. 2B ) being supplied to the thermal cracker.

After passing through pressure reducer valve 50 , some or all of the somewhat cooled thermally cracked stream may be supplied to the input to fractionator V 1 as indicated by broken line 41 in FIG. 2 A. In such case, the lighter fractions in the thermally cracked stream would be recovered from the overhead of fractionator V 1 , and the remaining portion of the thermal cracked stream, namely by-product asphaltenes, heavier fractions, and the unconverted DAO being part of the residue that passes out the bottom of fractionator V 1 . Preferably, however, recovery of the lighter fractions produced by the thermal cracking process takes place without feeding back the thermally cracked stream to the input 31 of the upgrader.

As shown in FIG. 3 , the cooled, and pressure reduced thermally cracked stream is applied to separator V 18 which produces two streams: at its overhead, a stream of thermal cracker atmospheric distillate (fractions with atmospheric equivalent boiling temperatures less than about 650° F. and gases) produced by the cracking process; and at its bottom, a stream of thermal cracker atmospheric residue (i.e., a stream of that which remains after atmospheric distillate is removed from the thermally cracked feed to the separator). The fluid flowing out the overhead of this separator is further cooled in heat exchanger E 23 before entering separator V 19 which serves to separate the feed into a vapor stream containing some atmospheric distillate and gas, and a liquid stream containing atmospheric distillate all produced by the thermal cracking process. The liquid stream of atmospheric distillate from separator V 19 is supplied to heat exchanger E 19 ( FIG. 2A ) where cooling takes place before this stream is delivered to condenser E 20 to join the virgin atmospheric distillate contained in feed 31 .

The vapor stream from separator V 19 may be cooled in heat exchanger E 25 for the purpose of preheating solvent for application to turbine T, and then condensed in condenser E 26 . After pressure reduction in a reducer valve, the overhead fluid from separator V 19 flows to separator V 20 which allows the non-condensable gases produced by the thermal cracking process to be drawn out the overhead of this separator and supplied, for example, to heater H 2 . The bottom fluid from separator V 20 , atmospheric distillate produced by the thermal cracking process, is delivered by pump P 14 to heat exchanger E 27 where it cools the output of mixer M 2 before being an input to this mixer.

The other input to mixer M 2 is the heaviest portions of the thermal cracker atmospheric residue stream produced at the bottom of separator V 18 . Such stream is applied to vacuum fractionator V 21 which produces two streams: at its overhead, a stream of thermal cracker vacuum distillate (i.e., fractions with atmospheric equivalent boiling points in the range 650-1000° F.) produced by the thermal cracking process; and at its bottom, a stream of thermal cracker vacuum residue (i.e., a stream of that which remains after vacuum distillate is removed from the thermal cracker atmospheric residue feed to the separator). The thermal cracker vacuum residue contains by-product asphaltenes, un-converted DAO, etc. Superheated steam may be injected into separator V 21 to assist in the fractionation process.

Pump P 15 delivers a stream of thermal cracker vacuum residue to mixer M 2 wherein the stream is mixed with thermal cracker atmospheric distillate to produce a mixture that is cooled in heat exchanger E 27 , and heated as needed in heat exchanger E 28 before being delivered to mixer M 3 . In this mixer, the heated mixture is combined with virgin asphaltenes in feed 31 delivered to mixer M 3 by pump P 5 at the outlet of stripper V 6 ( FIG. 2A ) of evaporation section 38 of SDA unit 18 ′. The output of mixer M 3 is a fuel oil blend that is comparable to conventional fuel oil produced by refineries by blending diesel fuel with the asphaltene product produced by an SDA unit.

The present invention also contemplates other uses for the thermal cracker atmospheric distillate produced at the overhead of separator V 18 , the thermal cracker atmospheric residue produced at the bottom of separator V 18 , and the vacuum thermally cracked stream, and the thermal cracker vacuum residue produced at the bottom of fractionator V 21 . For example, instead of producing a fuel oil blend, these components can be used to produce asphalt cement or asphalt cement binder.

The upgrader shown and described in FIGS. 2A , 2 B, and 3 receives crude oil at its input at 31 , and produces at point Z valuable light hydrocarbons (e.g., naphtha, virgin and thermal cracker produced atmospheric distillates, and virgin and thermal cracker produced vacuum distillates) for tankage or pipeline utilization, and at point Y, a fuel oil blend of the heavy residual material that remains after the valuable light hydrocarbons are removed from the feed. However, instead of storing or transporting the valuable light hydrocarbons produced by the upgrader apparatus, they may be directly used for power generation purposes as illustrated in FIGS. 4A , 4 B, 5 , 6 and 7 .

In apparatus 50 shown in FIG. 4A , upgrader 30 A is constructed in accordance with the present invention and receives hydrocarbon feed 51 which may be crude oil, vacuum resid from a refinery, or other heavy hydrocarbon. Upgrader 30 A produces two main outputs from this single input: non-asphaltene product stream 52 , which comprises light, valuable hydrocarbons (e.g., atmospheric and vacuum distillates, etc.) produced as described above, and asphaltene product stream 53 . Some or all of stream 52 is piped to prime mover 54 which may be, for example, an internal combustion engine such as a diesel engine, gas engine, or a gas turbine, etc., coupled to a generator (not shown) for generating power by using stream 52 as a fuel and producing hot exhaust gases in conduit 55 .

Some or all of asphaltene stream 53 is directed to combustor 56 wherein combustion takes place producing hot products of combustion in conduit 57 . Both all, or some of the exhaust from the prime mover and the hot products of combustion from the combustor are applied to steam boiler 58 which generates steam that is applied to steam turbine 59 for generating additional power. The heat depleted gases that exit the steam boiler are conveyed to a stack which may contain scrubber 60 that removes environmentally deleterious components such as sulfur before the heat depleted gases are vented to the atmosphere.

In apparatus 70 shown in FIG. 4B , upgrader 30 A is constructed in accordance with the present invention and receives hydrocarbon feed 51 which may be crude oil, vacuum resid from a refinery, or other heavy hydrocarbon. Upgrader 30 A produces two main outputs from this single input: non-asphaltene product stream 52 , which comprises light, valuable hydrocarbons (e.g., atmospheric and vacuum distillates, etc.) produced as described above, and asphaltene product stream 53 . Some or all of stream 52 is piped to prime mover 54 which may be, for example, an internal combustion engine such as a diesel engine, gas engine, or a gas turbine, etc., coupled to a generator (not shown) for generating power by using stream 52 as a fuel and producing hot exhaust gases in conduit 55 .

All or some of the exhaust gases are applied to fluidized bed combustor 71 (which, if preferred, may be a spouted bed combustor) as combustion air, or as a fluidizing medium, or as both as combustion air and as a fluidizing medium. The fuel for combustor 71 is the asphaltene in stream 53 produced by the upgrader. The hot combustion gases produced by the fluidized bed combustor are applied to steam boiler 72 which generates steam that is applied to steam turbine 73 which generates additional power. The heat depleted gases that exit the steam boiler are conveyed to a stack which may contain scrubber 74 that removes environmentally deleterious components such as sulfur before the heat depleted gases are vented to the atmosphere.

In apparatus 80 shown in FIG. 5 is a variant of the apparatus shown in FIG. 4B in that FIG. 5 shows gas turbine unit 54 A as the prime mover. Unit 54 A includes compressor 81 for compressing ambient air and producing a compressed air stream that is applied to burner 82 in which is burned a non-asphaltene product from the upgrader. Burner 82 produces a heated stream of gas that is applied to turbine 83 coupled to generator 84 . The heated stream of gas expands in turbine 83 driving the generator and producing power and exhaust gases. All or some of these exhaust gases are supplied to fluidized bed combustor 85 as a fluidizing medium and/or combustion air to support the combustion of asphaltene product produced by the upgrader.

Heat exchanger 86 interposed between compressor 81 and burner 82 is operatively associated with combustor 85 (which may be a fluidized bed combustor, or spouted bed combustor) for transferring heat from the combustor to the compressed air stream produced by the compressor. The hot combustion gases produced by combustor 84 are applied to steam boiler 87 which generates steam that is used by steam turbine 88 to generate additional power. The heat depleted gases that exit the steam boiler are conveyed to a stack which may contain scrubber 89 that removes environmentally deleterious components such as sulfur before the heat depleted gases are vented to the atmosphere.

In apparatus 90 shown in FIG. 6 , both an air turbine and a gas turbine are the prime movers that use the non-asphaltene product stream produced by upgrader 30 A. Gas turbine unit 91 of apparatus 90 includes compressor 92 for compressing ambient air and producing a compressed air stream, and burner 93 to which the compressed air stream is supplied and to which is supplied a non-asphaltene product from the upgrader. Burner 93 heats the air producing a heated stream of gas that is applied to gas turbine 94 coupled to generator 95 . The heated stream of gas expands in turbine 94 which drives the generator producing power and exhaust gases which are applied to waste heat boiler 103 for producing steam.

Apparatus 90 also includes air turbine unit 96 having compressor 97 for compressing ambient air and producing a compressed air stream, and heat exchanger 98 for heating the air and producing a heated stream of air. Air turbine 99 coupled to generator 100 is responsive to the heated stream of air for driving the generator and producing power and a heat-depleted stream of air. Combustor 101 , configured as a fluidized bed combustor, or spouted bed combustor, combusts asphaltenes from the product stream of asphaltenes produced by said upgrader, and produces combustion gases.

Heat exchanger 98 is operatively associated with and responsive to combustor 101 for supplying heat to the air stream compressed by compressor 97 . As indicated, the heat-depleted stream of air exhausted by turbine 99 supplies all, or some of the air for fluidizing the combustor. Finally, steam boiler 102 is responsive to the combustion gases from the combustor for generating steam, which together with steam from waste heat boiler 103 , is supplied to steam turbine 104 for generating additional power.

Optionally, oil shale, low grade coal, or other material, e.g., limestone, containing substantial amounts of calcium carbonate, can be combusted in the combustors shown in FIGS. 4A , 4 B, 5 , and 6 for effecting the capture of sulfur compounds in the asphaltene product stream burned in the various combustors. In a further embodiment of the invention shown in FIG. 7 , waste heat produced by a power generating system, such as a system that includes a prime mover such as a combustion turbine, and/or internal combustion engines (e.g., diesel engine, gas engine, etc.), or a combined cycle system having a steam turbine, can be utilized to provide process heat for a conventional solvent deasphalting unit, or for the upgraders disclosed in this application.

When gases from the prime mover are added to the combustor or steam boiler, pollutants (e.g., sulfur, etc.) of both streams can be treated using a common system, e.g., by adding limestone, oil shale, low grade fuel, etc. to the combustor. In such a manner, sulfur rich fuel can be used in the gas turbine, the sulfur being treated in the combustor to which all or a portion of the exhaust gases of the gas turbine are added.

The advantages and improved results furnished by the method and apparatus of the present invention are apparent from the foregoing description of the preferred embodiments of the invention. Various changes and modifications may be made without departing from the spirit and scope of the invention as described in the appended claims.

Claims

1. Apparatus for upgrading a hydrocarbon source feed, comprising:a) a fractionator for receiving a first hydrocarbon input stream and separating the same into fractions with an atmospheric equivalent boiling temperature less than about Tf °F. (Tf− fractions) thereby producing a product stream that consists of Tf− fractions, and a residue stream (Tf+ stream); b) a solvent deasphalting (SDA) unit utilizing a solvent having a critical temperature Tc for receiving a second hydrocarbon input stream which includes said residue stream for producing a first product stream of substantially solvent-free asphaltenes, and a second product stream containing substantially solvent-free deasphalted oil (DAO), and wherein Tf is greater than about Tc−50° F., such that said source feed is included in said first or second input streams; c) a thermal cracker for thermally cracking the DAO in said second product stream for producing an output stream that includes thermally cracked fractions and by-product asphaltenes produced by thermally cracking the DAO, whereby at least some of said thermally cracked fractions are fed back to said first input stream; and d) a prime mover operating on a non-asphaltene product stream produced by said apparatus for generating power and exhaust gases, wherein said apparatus is responsive to heat contained in said exhaust gases.

2. A method for upgrading a hydrocarbon source feed comprising the steps of:a) deasphalting said hydrocarbon source feed using a solvent deasphalting unit utilizing a solvent having a critical temperature Tc with an atmospheric boiling temperature greater than about Tf °F. that receives said hydrocarbon source feed for producing a substantially solvent-free asphaltene product, and a substantially solvent-free nonasphaltene product in response to input heat of at least about Tf° F., and wherein Tf is greater than about Tc−50° F.; b) generating power using a prime mover that generates power and produces waste heat; and c) utilizing said waste heat to provide said input heat.

3. Apparatus for upgrading a hydrocarbon source feed, comprising:a) a fractionator for receiving a first hydrocarbon input stream and separating the same into fractions with an atmospheric equivalent boiling temperature less than about Tf °F. (Tf− fractions) thereby producing a product stream that consists of Tf− fractions, and a residue stream (Tf+ stream); b) a solvent deasphalting (SDA) unit utilizing a solvent having a critical temperature Tc for receiving a second hydrocarbon input stream which includes said residue stream for producing a first product stream of substantially solvent-free asphaltenes, and a second product stream containing substantially solvent-free deasphalted oil (DAO), and wherein Tf is greater than about Tc−50° F., such that said source feed is included in said first or second input streams; c) a thermal cracker for thermally cracking the DAO in said second product stream for producing an output stream that includes thermally cracked fractions and by-product asphaltenes produced by thermally cracking the DAO, whereby at least some of said thermally cracked fractions are fed back to said first input stream; and d) a combustor for combusting the solvent-free asphaltenes from the solvent deasphalting unit, thereby producing hot products of combustion and generating heat for use in producing steam.

4. A method for upgrading a hydrocarbon source feed comprising the steps of:a) deasphalting said hydrocarbon source feed using a solvent deasphalting unit utilizing a solvent having a critical temperature Tc with an atmospheric boiling temperature greater than about Tf °F. that receives said hydrocarbon source feed for producing a substantially solvent-free asphaltene product, and a substantially solvent-free nonasphaltene product in response to input heat of at least Tf °F., and wherein Tf is greater than about Tc−50° F.; b) generating power using a prime mover that generates power and produces waste heat; and c) combusting the solvent-free asphaltenes from the deasphalting step in a combustor, thereby producing hot products of combustion and generating heat for use in producing steam.