Patent Application
20110198265
The invention is an innovative hydroconversion processing configuration for converting bitumen or heavy oils and producing finished products and/or synthetic crude oil (SCO). The novel process configuration is self-sufficient for the required hydrogen and there is no heavy unconverted residue or coke product to dispose of using the disclosed process.
The invention results in a high yield of specification SCO which will not contain any undesirable asphaltenes, no undesirable bottoms or coke product, and is accomplished with minimal investment and operating costs. SCO is the output from a bitumen/extra heavy oil upgrader facility used in connection with oil sand production. It is also the output from an oil shale extraction. The properties of the SCO depend to a large extent on the processes used in the upgrading. High quality SCO is typically low in sulfur, has an API gravity in the range of 32-38° and is also known as “upgraded crude”.
The world's higher quality light natural crude oils are those generally having an API gravity of 35 to 45° with sulfur content less than 0.5 percent. These high quality light natural crudes cost the least to refine into a variety of highest value end products including petrochemicals and therefore command a price premium. More importantly, however, the majority of world refinery capacity is geared to a high proportion of light natural crude oils with an API gravity of approximately 38° or higher.
It is generally accepted that world supplies of light crude oils recoverable by the conventional means of drilling wells into reservoirs and the use of nature's pressure, or by pumping to recover the oil, will be diminished to the extent that in the coming decades these supplies will no longer be capable of meeting the world demand.
To find relief from oil supply shortage it will be necessary to substantially increase processing of the vast world reserves of coal and viscous oil, bitumens in tar sands and kerogens in oil shale. These sources of crude oil remain largely unexploited today although recovery of oil from tar sands is in practice in Canada. The development of technology for the production of synthetic oil as an alternative to the light crude oil found in nature continues to be plagued by the large capital investments required in recovery and production facilities and a long wait for return on investment. In addition, large expenditures are required to construct or retrofit refineries for synthetic oils recovered from heavy oils and bitumens. In addition, present synthetic oil plants for processing heavy oils, or bitumens from tar sands, have focused more on the development of systems for recovery and production than on energy efficiency, maximization of yield, and high environmental processing standards. Except for South Africa's Sasol process, which benefits from low cost labor used in coal mining, coal liquefaction is not yet cost competitive with synthetic oil produced from tar sands bitumen or heavy oils.
It is therefore of considerable importance that ways are found to produce light synthetic crudes comparable in quality to the rapidly depleting reserves of light natural crudes available from conventional sources and at a cost at least approaching these crudes and fully competitive with the crudes being recovered at higher cost from under the sea or from frontier areas such as the extreme north with its rigorous climate. It is also important that light synthetic crudes are comprised in desired proportions of a mixture of aromatic, naphthenic and paraffinic components as these three families of compounds comprise essential feedstock to refinery capacity producing today's transportation fuels and feedstocks for the petrochemical industry.
Accordingly, applicants have disclosed an invention which is an innovative processing configuration for converting these heavy oils and/or bitumens to produce a transportable SCO. In the invention, the heavy oil or bitumen feedstock is processed with no net bottoms product (residue, coke), thereby eliminating a potential disposal problem. Moreover, the configuration maximizes liquid yield and balances the hydrogen requirements utilizing the gasification of residue products.
In this invention, the heavy oil or bitumen feedstock is initially fractionated in a combination of crude and vacuum stills to produce a straight-run atmospheric gas oil (AGO) feedstream, an atmospheric residue feedstream, straight run vacuum gas oil (VGO) feedstream and a vacuum residue feedstream. Typically, the heavy oil or bitumen is highly viscous and is diluted with light oil in order to be transported from the field. This light oil is distilled in the crude atmospheric still and is returned to the field. ‘A portion of the vacuum residue feedstream is thereafter fed to a first high-pressure, ebullated-bed reactor system along with hydrogen from a downstream hydrogen plant to create distillate, VGO, and unconverted vacuum residue streams. The VGO and distillate streams from the ebullated-bed reactor system are thereafter combined with the straight-run AGO and VGO streams from the crude and vacuum stills and sent to traditional fixed-bed hydrotreating and hydrocracking units.
The unconverted vacuum residue is combined with the portion of the vacuum residue from the crude vacuum still that was not sent to the first ebullated-bed reactor system and sent to a solvent deasphalting unit (SDA). The SDA unit produces a deasphalted oil (DAO) stream and an asphaltene stream. The DAO stream is processed along with a hydrogen stream in a second, lower pressure, ebullated-bed reactor system which operates at high severity and converts in excess of eighty-five (85%) percent of the DAO into distillates and VGO. These distillate and VGO products are thereafter blended with the products from the fixed-bed hydrotreating and hydrocracking reactors to create a synthetic crude oil (SCO). The small fraction of DAO that is not converted in the second ebullated-bed reactor is thereafter routed to a gasification plant or can be blended into the final SCO product.
The asphaltene stream from the SDA unit and the small quantity of unconverted DAO from the second ebullated-bed reactor system are sent to the gasification plant to produce the required hydrogen for the two ebullated-bed reactor systems and the secondary hydrotreating/hydrocracking units.
These and other features of the present invention will be more readily apparent from the following description with reference to the accompanying drawing.
An objective of the invention is to provide an innovative processing configuration for maximizing liquid SCO yield and balancing hydrogen requirements utilizing gasification of residues produced from the process.
Another objective of the invention to allow the processing of bitumen or heavy oil with no net bottoms product (residue, coke), which can present a disposal problem.
It is a further objective of the present invention to utilize maximum size and throughput ebullated-bed reactor systems for the vacuum residue and DAO processing as well as for the SDA and gasification plants to provide maximum total heavy oil or bitumen feedrate and maximum resulting SCO production.
It is another objective of the invention to utilize lower pressure ebullated-bed hydroconversion to enable high conversion of the DAO for direct blending of the second ebullated-bed products into the final SCO product.
In this invention, the heavy oil or bitumen feedstock is initially fractionated in a combination of crude and vacuum stills to produce light diluent, straight-run atmospheric gas oil (AGO) feedstream, an atmospheric residue feedstream, straight run vacuum gas oil (VGO) feedstream and a vacuum residue feedstream. The light diluent, used to transport the heavy oil or bitumen, is returned to the field. A large portion of the vacuum residue feedstream is thereafter fed to a first ebullated-bed reactor unit along with hydrogen from a downstream hydrogen plant to create distillate, VGO, and unconverted vacuum residue streams. The VGO and distillate streams from the ebullated bed reactor system are thereafter combined with the straight-run AGO and VGO streams from the vacuum and crude stills and sent to traditional fixed-bed hydrotreating and hydrocracking units for further refinement.
The unconverted vacuum residue from the ebullated-bed system is combined with the portion of the vacuum residue from the vacuum still that was not sent to the first ebullated-bed reactor and sent to a solvent deasphalting unit (SDA). The SDA produces a deasphalted oil (DAO) stream and an asphaltene stream. The DAO stream is processed along with a hydrogen stream in a second, lower pressure ebullated-bed reactor system which operates at high severity and converts in excess of eighty-five (85%) percent of the DAO into distillates and VGO. These distillate and VGO products do not require secondary hydrotreatment and are thereafter blended with the products from the fixed-bed hydrotreating and hydrocracking reactors to create a synthetic crude oil (SCO). The small quantity of DAO that is not converted in the second ebullated-bed reactor system is thereafter routed to a gasification plant or can be blended into the final SCO product.
The asphaltene stream from the SDA unit and optionally the unconverted DAO from the second ebullated-bed reactor system are sent to the gasification plant to produce the required hydrogen for the two ebullated-bed units and the secondary hydrotreating/hydrocracking units. The primary variable for insuring that the required quantity of hydrogen is produced in the gasification plant is the fraction of the vacuum residue which bypasses the first ebullated-bed reactor system.
More particularly, the present invention describes a process for converting high percentages of heavy oil or bitumen feedstocks and producing a high yield of SCO comprising:
In one embodiment a portion of the atmospheric residue stream from step a) is sent directly into the solvent deasphalter of step d) along with the straight run vacuum residue streams.
In another embodiment between 0% and 80% percent of the straight run vacuum residue stream from step b) bypasses said first ebullated-bed reactor system in step c) and is sent directly to the solvent deasphalting unit in step d).
In still another embodiment a portion of the distillate stream and vacuum gas oil streams from step e) are not included in the synthetic crude oil product.
In another embodiment a portion of the unconverted deasphalted oil stream from step e) is utilized in the synthetic crude oil of step g).
In one embodiment, the straight run distillates and vacuum gas oil from steps a) and b) and the conversion distillates and VGO from step c) can be blended directly into the SCO product if a lower quality SCO product is desired.
In another embodiment, the gasification complex in step h) can produce power for internal or external usage, or can produce a synthetic gas.
Butanes which are created by the first ebullated-bed reactor system, the second ebullated-bed reactor system, or the series of hydrotreatment and hydrocracking reactors, can be blended in step h) at greater than one volume percent with said hydrotreated C5+ product from step f), said distillate stream and said vacuum gas oil stream from step e) to create a synthetic crude oil.
The heavy oil or bitumen feedstream has the following properties: API gravity less than 15°, sulfur content greater than 3 W % and vacuum residue content greater than 35%.
In an embodiment, a portion of the atmospheric residue stream bypasses the vacuum still and can be fed to the ebullated-bed unit along with the vacuum residue stream. Additionally, in a preferred embodiment the ebullated-bed reactor operates at the following range of conditions: reactor total pressure of 1,500 to 3,000 psia, reactor temperature of 750 to 850° F., hydrogen feedrate of 1,500 to 10,000 SCF/Bbl, liquid hourly space velocity of 0.1 to 1.5 hr−1, and a daily catalyst replacement rate of 0.1 to 1.0 lb/Bbl of feedstock.
Generally such hydroprocessing is in the presence of catalyst containing group VI or VIII metals such as platinum, molybdenum, tungsten, nickel, cobalt, etc., in combination with various other metallic element particles of alumina, silica, magnesia and so forth having a high surface to volume ratio. More specifically, catalyst utilized for hydrodemetallation, hydrodesulfurization, hydrodenitrification, hydrocracking etc., of heavy oils and the like are generally made up of a carrier or base material; such as alumina, silica, silicaalumina, or possibly, crystalline aluminosilicate, with one more promoter(s) or catalytically active metal(s) (or compound(s)) plus trace materials. Typical catalytically active metals utilized are cobalt, molybdenum, nickel and tungsten; however, other metals or compounds could be selected dependent on the application. The ebullated-bed reactor system maybe comprised of one, two or three stages in series and may incorporate phase separation between the reactor stages to offload the gas from the first stage reactor.
The SDA unit may be operated with a C3/C4/C5 solvent to obtain a high DAO yield. The solvent deasphalting conditions include a temperature from about 50° F. (10° C.) to about 600° F. (315° C.) or higher, but the deasphalter operation is preferably performed within the temperature range of 100° F. (38° C.) to 400° F. (204° C.). The pressures utilized in the solvent deasphalter are preferably sufficient to maintain liquid phase conditions. A broad range of pressures from about 100 psig (689 kPag) to 1,000 psig (6,900 kPag) are generally suitable with a preferred range being from about 200 psig (1,380 kPag) to 600 psig (4,140 kPag).
In the process according to the invention, the conversion percentage of the feedstream processed in the first ebullated-bed reactor hydrocarbon feedstream can be greater than 50% wt, and may even be greater than 60% wt. In the second ebullated-bed reactor system, the conversion percentage of the feedstream processed is preferably greater than 70% wt and more preferably greater than 75% wt.
Additionally, in the process according to the invention, the overall volumetric synthetic crude oil yield rate as a fraction of heavy oil or bitumen but not including diluents feedrate is greater than 90% and can be greater than 95%. Moreover, the residue conversion percentage in step c) is greater than 50% wt., preferably greater than 60% wt. The deasphalted oil conversion on a vacuum residue basis in step e) is greater than 70% wt and may even be greater than 80% wt. or 90% wt.
The heavy oil or bitumen stream 10 enters the plant battery limits. Typically, this stream has API gravity less than 15° and requires 10-40% light diluent to transport from the field to the processing complex. The heavy oil or bitumen feedstream 10 is first processed through a crude atmospheric fractionator 12 to create an atmospheric residue stream 14 nominally boiling above 650° F. and straight run atmospheric gas oil (AGO) stream 15 and a diluent stream 11 which is returned to the field.
The atmospheric residue stream 14 from the crude atmospheric fractionator 12 is thereafter sent to a vacuum fractionator 16 to create a vacuum residue stream 18 nominally boiling above 975° F. and a straight run vacuum gas oil (VGO) stream 20 boiling between 650 and 975° F. Although not shown in the drawing, depending upon the plant capacity and/or economics, it is possible that a portion of the atmospheric residue stream 14 can bypass the vacuum fractionators 16 and be fed directly to the solvent deasphalter 25. The straight run VGO stream 20 and the straight run AGO stream 15, are thereafter routed to traditional fixed-bed hydrotreating and hydrocracking units 30. These secondary hydroprocessing units typically operate at moderate temperature and pressure and create a distillate plus VGO stream 32 which will be stable and contain acceptable level of sulfur, nitrogen and aromatics. Although not shown in
A portion of the vacuum residue stream 18 is thereafter sent to a first ebullated-bed reactor system 19 to create a distillateNGO product stream 21 and an unconverted vacuum residue stream 22. The residue conversion percentage in this first ebullated-bed reactor system 19 is generally greater than 50% wt. The distillate NGO product stream 21 is thereafter routed along with the straight run VGO stream 20 and the straight run AGO stream 15 to traditional fixed-bed hydrotreating and hydrocracking units 30, although it is possible to blend the distillate/VGO product stream 21 directly into the SCO product 36 and bypass the traditional fixed-bed hydrotreating and hydrocracking units 30 depending upon the desired quality of the SCO product.
The unconverted vacuum residue stream 22 is combined with the portion of the crude still vacuum residue stream 18 that was not sent to the first ebullated-bed reactor 19, shown in this schematic as 18a, and sent to a solvent deasphalting unit 25 where it is separated into deasphalted oil (“DAO”) stream 28 and an asphaltene stream 26. Generally, the portion of the crude still vacuum residue stream not sent to the first ebullated-bed reactor 18a is between 0 and 80%.
The solvent utilized in the SDA unit 25 may be any suitable hydrocarbonaceous material which is a liquid within suitable temperature and pressure ranges for operation of the countercurrent contacting column, is less dense than the feed streams 18a, 22, and has the ability to readily and selectively dissolve desired components of the feed streams 18a, 22 and reject the asphaltic materials also commonly known as pitch or asphaltenes. The solvent may be a mixture of a large number of different hydrocarbons having from 3 to 14 carbon atoms per molecule, such as light naphtha having an end boiling point below about 200° F. (93° C.).
Preferably, the SDA unit 25 is operated with a C3/C4/C5 solvent to obtain a high DAO yield such that the DAO can be treated in a classic fixed-bed reactor or in an ebullated-bed unit. More specifically, the solvent may be a relatively light hydrocarbon such as ethane, propane, butane, isobutane, pentane, isopentane, hexane, heptane, the corresponding mono-olefinic hydrocarbons or mixtures thereof. Preferably, the solvent is comprised of paraffinic hydrocarbons having from 3 to 7 carbon atoms per molecule and can be a mixture of 2 or more hydrocarbons. For instance, a preferred solvent may be comprised of a 50 volume percent mixture of normal butane and isopentane.
The solvent deasphalting conditions include a temperature from about 50° F. (10° C.) to about 600° F. (315° C.) or higher, but the solvent deasphalter 25 operation is preferably performed within the temperature range of 100° F. (38° C.)-400° F. (204° C.). The pressures utilized in the solvent deasphalter 25 are preferably sufficient to maintain liquid phase conditions, with no advantage being apparent to the use of elevated pressures which greatly exceed this minimum. A broad range of pressures from about 100 psig (690 kPag) to 1,000 psig (6,900 kPag) are generally suitable with a preferred range being from about 200 psig (1,380 kPag) to 600 psig (4,140 kPag). In the SDA Unit, an excess of solvent to charge stock should preferably be maintained. The solvent to charge stock volumetric ratio should preferably be between 2:1 to 20:1 and preferably from about 3:1 to 9:1. The preferred residence time of the charge stock in the solvent deasphalter 11 is from about 10 to about 60 minutes.
The asphaltene stream 26 from the solvent deasphalter unit 25 is sent to a gasification complex 27 where it produces hydrogen stream 29 that is required for the for the two ebullated-bed reactor systems 19 & 31 and for the hydrotreating/hydrocracking units 30. The gasification complex includes the gasification reactors, gas clean-up, shift reactors, carbon dioxide separation and recovery, hydrogen purification and air separation plants. Moreover, depending upon the plant economics and/or requirements, the gasification complex can optionally produce power and/or medium BTU syngas for the upgrader and upstream resource recovery.
The DAO stream 28 from the solvent deasphalting reactor unit 25 is thereafter sent to a second ebullated-bed reactor system 31 for hydroconversion. The hydrogen required for this second ebullated-bed reactor 31 is also obtained from the hydrogen stream 29 created by the gasification complex 27.
The second ebullated-bed reactor system 31 is a high conversion ebullated-bed hydroconversion unit. The DAO stream 28 is catalytically hydrocracked and hydrotreated in the ebullated-bed reactor 31 system and converts greater than 70% of the DAO feedstream 28 and creates a distillate plus VGO stream 34. Stream 34 is thereafter combined with the hydrotreated distillates and VGO stream 32 from the fixed-bed hydrotreater and hydrocracking reactors 30 to create the final SCO product 36. Although not shown in
This invention will be further described by the following example, which should not be construed as limiting the scope of the invention.
A flowrate of 300,000 BPSD of bitumen is processed in the example. The rate does not include the light diluent which is used to transport the crude from the field. The bitumen is fed to an atmospheric still which produces the light diluent (returned to the field), 43,400 BPSD of straight run atmospheric gas oil (SRAGO), and 256,600 BPSD of atmospheric residue. The atmospheric residue is sent to the vacuum fractionator to produce a vacuum residue stream (167,500 BPSD) along with 89,100 BPSD straight run vacuum gas oil (SRVGO) stream. The SRAGO and SRVGO are routed to traditional fixed-bed hydrotreating and hydrocracking units, respectively. These values and other flowrates are shown in Table 1.
The vacuum residue stream from the vacuum fractionator is split between an ebullated-bed hydroconversion unit and a solvent deasphalting unit. The split is determined by attaining a hydrogen-balanced plant. In this example, of the total 167,500 BPSD of straight run vacuum residue, 134,000 BPSD is routed to the first ebullated-bed reactor system and 33,500 BPSD is routed to the SDA Unit.
The feedrate to the vacuum residue ebullated-bed unit is 134,000 BPSD and is the maximum rate for a specified maximum reactor size. This reactor size is normally limited by either fabrication or transportation constraints. In a pre-invention processing configuration, the total heavy crude rate would be that equivalent to the 134,000 BPSD of vacuum residue or 240,000 BPSD. The invention results in the processing of an additional 60,000 BPSD of heavy crude (300,000 versus 240,000 BPSD). The vacuum residue ebullated-bed operates at a residue conversion level near the maximum desired for the particular feedstock. The ebullated-bed distillate and VGO products require additional treatment and are sent to secondary hydrotreating/hydrocracking units. As shown in Table 1, the first ebullated-bed unit produces 54,700 BPSD of naphtha/diesel and 36,900 BPSD of VGO. The unconverted ebullated-bed vacuum residue (46,900 BPSD) is sent, along with the remaining straight run vacuum residue (33,500 BPSD), to a solvent deasphalting (SDA) Unit.
The total SDA Unit feedrate is 80,400 BPSD. The feed is straight run vacuum residue (33,5.00 BPSD) and unconverted vacuum residue from the ebullated-bed unit (46,900 BPSD). Typically a butane or pentane solvent is utilized in the SDA Unit to produce deasphalted oil (DAO) and an asphaltene stream. In this example, the SDA Unit produces 55,000 BPSD of DAO and 25,400 BPSD of asphaltenes. The DAO, which contains significant levels of CCR and metals could be blended into the SCO product but would result in a significant decrease in the SCO quality and resultant value. Instead, in the disclosed invention, the DAO is processed in a second ebullated-bed unit.
The second ebullated-bed reactor operates at high severity and converts over 85 percent of the DAO into distillates and VGO. The resultant naphtha/diesel (32,800 BPSD) and VGO (18,700 BPSD) from this second ebullated-bed reactor system are sufficiently hydrogenated that they can be directly blended in the final SCO product. The unconverted DAO product is 7,700 BPSD. This small quantity of unconverted DAO is routed to the gasification unit. Alternatively this small quantity of hydrogenated DAO could be added to the SCO product if the small decrease in SCO quality/value would indicate favorable plant economics.
The gasification plant is fed the SDA asphaltenes (25,400 BPSD) and the unconverted DAO (7,700 BPSD) from the second ebullated-bed reactor unit. This gasification complex produces 509 MMSCFD of hydrogen, which is that, required for the first and second ebullated-bed units and the fixed-bed hydrotreating/hydrocracking units. The gasification plant in this example does not produce any excess syngas, which could be utilized to produce power for the upgrading facilities. This could be included in the gasification design and would impact the vacuum residue split, SDA solvent utilized and SCO yield.
Table 2 shows the components of the final SCO blend and important inspections. The SCO is comprised of the hydrotreating/hydrocracking effluents, the second ebullated-bed C5-975° F. effluent and butanes at 1 V %. The SCO rate is 286,900 kBPSD with 33.2° API gravity and less than 0.1 W % sulfur. The SCO contains a high percentage of desirable mid-distillate boiling material (43.1 V %) and no material boiling greater than 975° F. The SCO liquid yield as a percentage of the crude rate is 95.6 V %. This is a high value when considering that a portion of the heavy crude/bitumen is utilized to produce the required hydrogen.
The maximization of crude and SCO rates for a maximum size primary upgrading unit (ebullated-bed) is a key element of the invention. For a typical process configuration (pre-invention), all of the straight run vacuum residue would be processed in the vacuum residue ebullated-bed and the feedstock throughput would be significantly limited. The pre-invention SCO yield would be approximately 90 V % versus the nearly 96 V % yield for the invention example.
The invention described herein has been disclosed in terms of specific embodiments and applications. However, these details are not meant to be limiting and other embodiments, in light of this teaching, would be obvious to persons skilled in the art. Accordingly, it is to be understood that the drawings and descriptions are illustrative of the principles of the invention, and should not be construed to limit the scope thereof.
