High conversion partial upgrading process

PATENT
High conversion partial upgrading process
United States Patent Application 20110155639
Inventors: Colyar, James J. (Newtown, PA, US)
Application Number: 12/655242 Publication Date:06/30/2011
FIELD OF THE INVENTION
The described invention discloses an innovative hydroconversion processing configuration for converting bitumen or heavy oils to produce a transportable synthetic crude oil (SCO). The innovative processing scheme disclosed herein maximizes the SCO yield at a minimal investment compared to currently known methods. SCO is the primary product from a bitumen/extra heavy oil upgrader facility and is typically associated with oil sands production.

SCO can also be the output from an oil shale extraction process. The properties of the synthetic crude depend to a large extent on the feedstock quality and on the processes used in the upgrading. Relative to the feedstock, SCO is lower in sulfur, has API gravity in the range of 20° to 35°, and is also known as “upgraded crude”.

The total heavy oil or bitumen feedstock is initially fractionated in a crude still to produce straight-run atmospheric gas oil (AGO), atmospheric residue (AR), and the light diluent which is used to transport the bitumen or heavy oil from the field. The diluent is returned to the field. A portion of the AR stream is sent to a vacuum still to produce straight run vacuum gas oil (VGO) and a vacuum residue feedstream. A portion of the AR may also be sent directly to the conversion unit. The vacuum residue feedstream and/or a portion of the atmospheric residue feedstream are thereafter processed along with a hydrogen stream in an ebullated-bed reactor system operating at relatively high severity conditions to produce a greater than seventy (70%) percent conversion rate of the vacuum residue. The ebullated-bed products, including distillates and unconverted vacuum residue, are thereafter blended with the heavy oil or bitumen AR which was by-passed and the fractionated straight run distillates (AGO and VGO) to produce the final SCO product.

Once the level of severity (primarily vacuum residue conversion level) in the ebullated-bed unit is set, the fraction of the heavy oil or bitumen AR that bypasses the vacuum fractionation and conversion unit can be set to attain the required final SCO qualities. Hydrogen for the ebullated-bed unit can be obtained via a natural gas-steam reformer or via gasification of a portion of the ebullated-bed heavy product or straight run vacuum residue. The invention results in a high yield of specification SCO, no undesirable bottoms or coke product and is accomplished with minimal investment and operating costs. Unlike much of the SCO commercially produced, the invention SCO will contain both straight run and conversion vacuum residue. The SCO will be stable as a result of the selection of optimal operating conditions in the ebullated-bed conversion unit and the proper blending technique to combine the bypassed bitumen/heavy oil AR and the conversion products.

BACKGROUND OF THE INVENTION
The world's higher quality light natural crude oils are those generally having an API gravity greater than 30° 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 important, however, world refinery capacity is geared to a high proportion of light natural crude oils with an API of 30° 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, straight 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 methods are found to produce synthetic crudes to replace the rapidly depleting reserves of light natural crudes available from conventional sources and at a cost at least approaching these crudes and 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 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 hydroconversion processing configuration for converting these heavy oils and/or bitumens to produce a transportable synthetic crude oil. In the invention, the atmospheric residue from the heavy oil or bitumen feedstock is only partially processed in the hydroconversion unit, there is no secondary hydrotreating nor is there any heavy unconverted residue or coke to dispose of using this novel process.

The entire heavy oil or bitumen feedstock is first fractionated in a crude still and thereafter a portion of the straight run atmospheric and/or vacuum residue created in the fractionation process is fed to an ebullated-bed hydroconversion reactor along with a hydrogen stream. The ebullated-bed reactor operates at relatively high severity and gives a conversion rate of greater than seventy (70%) percent. The converted products (975° F.) from the ebullated-bed reactor is thereafter mixed with straight-run distillates, by-passed heavy oil, bitumen atmospheric residue, and unconverted vacuum residue to create the final synthetic crude product.

These and other features of the present invention will be more readily apparent from the following description with reference to the accompanying drawing.

SUMMARY OF THE INVENTION
An objective of the invention is to provide an innovative processing configuration for maximizing feedstock capacity and liquid SCO yield at minimal required investment.

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 a maximum size and throughput ebullated-bed reactor for maximum total heavy oil or bitumen feedrate and SCO production. It is another object of the present invention to effectively blend the high conversion ebullated-bed unconverted residue and straight run heavy oil or bitumen so as to ensure the stability of final SCO product.

It is yet another object of the present invention to utilize this innovative configuration and substantially increase the efficiency of a processing system relative to traditional bitumen or heavy crude processing.

The heavy oil or bitumen feedstock is initially fractionated in crude still to produce straight-run AGO, atmospheric residue, and diluent which is returned to the field. The diluent is added to the raw bitumen at the field in order to transport the blend to the processing complex. A portion of the atmospheric residue is then sent to a vacuum still for further fractionation and the production of a straight run VGO and a vacuum residue stream. The vacuum residue feedstream and/or the atmospheric residue feedstream is thereafter processed along with a hydrogen stream in an ebullated-bed reactor system operating at relatively high severity conditions to produce a greater than seventy (70%) percent conversion rate. Multiple ebullated-bed reactors may be operated in series in accordance with this invention. The ebullated-bed products are thereafter blended with the atmospheric residue which was by-passed and the straight run distillates (VGO and AGO) to produce a stable and compatible synthetic crude oil.

Once the level of severity in the ebullated-bed unit is set, the fraction of the straight run atmospheric residue that bypasses the vacuum fractionation and conversion unit can be set to attain the required final SCO qualities. Hydrogen for the ebullated-bed unit can be obtained via a natural gas-steam reformer or via gasification of a portion of the ebullated-bed heavy product or straight run vacuum residue. The invention results in a high yield of specification SCO, no undesirable bottoms or coke product and is accomplished with minimal investment and operating costs.

More particularly, the present invention describes a novel process configuration for converting of heavy oil or bitumen feedstocks to high value, transportable synthetic crude oil comprising:

a) feeding a bitumen or heavy oil feedstock to an atmospheric fractionator to provide an atmospheric residue stream, a straight run atmospheric gas oil stream and a diluent stream used for transportation; and
b) feeding a portion of said atmospheric residue stream to a vacuum fractionator to create a vacuum residue stream and a straight run vacuum gas oil stream; and
c) feeding the vacuum residue stream and some or none of the atmospheric residue stream that was not processed in the vacuum fractionator in step b), along with a hydrogen stream to an ebullated-bed reactor system to create an unconverted residue stream, a full range distillate product stream, and a recovered butanes stream; and
d) blending a portion of the atmospheric residue stream that was not processed in the vacuum still of step b) or the ebullated-bed reactor system of step c) with the unconverted residue from the ebullated-bed reactor system of step c); and
e) blending the stream from step d) with the straight run atmospheric gas oil stream, straight run vacuum gas oil stream, the full range distillate product stream and the recovered butanes stream from the ebullated-bed reactor system to produce a transportable synthetic crude oil product.

In a preferred embodiment 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 a preferred embodiment, a portion of the atmospheric residue stream bypasses the vacuum still and is fed to the ebullated bed unit along with the vacuum residue stream. In a preferred embodiment, between 10 and 80 percent of the straight run atmospheric residue is bypassed. In a preferred embodiment, a portion of the straight run AGO or VGO streams or the ebullated-bed distillates are not included in the synthetic crude. In another preferred embodiment, the gas oils are hydrotreated or hydrocracked prior to be blended into the synthetic crude oil.

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.

In the process according to the invention, the overall conversion percentage of the feedstream processed in the ebullated-bed reactor hydrocarbon feedstream is preferably greater than 50% wt, and more preferably greater than 70%, and even more preferably greater than 75%.

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