Note: Descriptions are shown in the official language in which they were submitted.
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CA 02570231 2006-12-04
A METHOD FOR PROCESSING OIL SAND BITUMEN
FIELD OF THE INVENTION
This invention relates to a method for processing oil sand bitumen, in
particular to a
method for processing oil sand bitumen to enhance the pipeline transmission
performance
thereof.
BACKGROUND OF THE INVENTION
Oil sand bitumen is actually a highly viscous asphalt, characterized in a high
density
(0.97-1.015 glcm3 at normal temperature and under normal pressure), a high
viscosity
(generally 100000-1000000 cSt at room temperature), and high contents of
sulfur,
asphaltenes and nickel and vanadium. The oil sand bitumen averagely comprises
83.2%
carbon element and 10.4% hydrogen element with a very high C/H ratio and a
high viscosity
and almost cannot flow at ambient temperature.
Currently the oil sand bitumen is mined mainly by the following three
processes:
1. Cyclic Steam Stimulation. In this process, a high-pressure steam is
injected into
the oil sand layer and remains there for several weeks. The heat can soften
the bitumen, while
the steam can dilute the bitumen and separate it from the sand, and then the
bitumen capable
of flowing is pumped onto the ground.
2. Steam Assisted Gravity Drainage. In this process, two parallel wells are
drilled in
the oil sand layer with one well located upper and the other located lower,
and steam is
continuously injected into the upper well. When oil sand layer is heated by
the steam, the oil
sand is softened and flows to the lower well by gravity and then can be pumped
onto the
ground.
3. Open Pit mining. In this process, the bitumen-containing oil sand is
excavated by
machine and then is flushed with solvent and caustic water, and the mixtures
of oil and
bitumen strip from the sand particles or the mixtures of caustic water and
bitumen are
evaporated to remove the solvent or water to yield oil sand bitumen.
The oil sand bitumen obtained by the above-mentioned three processes can be
upgraded via hydrogenation or decarbonization followed by conventional crude
oil
processing to yield oil and petrochemical products. The main refining
processes adopted
hereof comprise the atmospheric distillation, vacuum distillation, and the
delayed coking
followed by hydrofining or hydrotreating to route the products to the blending
unit in order to
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CA 02570231 2006-12-04
manufacture the Synthetic Crude Oil (SCO), which can be processed at oil
refining
enterprises to yield commodity oil products such as fuel oil, lubricating oil,
asphalt and
petrochemicals needed by the market.
Since the oil sand bitumen almost cannot flow at normal temperature because of
its
extremely high viscosity, it is necessary to upgrade the oil sand bitumen at
the mining site to
reduce its viscosity or improve its quality to meet the requirements for
pipeline transmission
so that the oil sand bitumen can be available on the market to play its role.
Currently, the
method for processing the oil sand bitumen mainly comprises the method of
mixing the
bitumen with a diluting agent to reduce the viscosity of oil sand bitumen.
This method is
performed by mixing the oil sand bitumen with a diluting agent at the oilfield
and
transmitting this mixture in pipeline, at the terminal of which the oil sand
bitumen in
admixture with the diluting agent is either handed over to the end user, or
the diluting agent is
reclaimed and reused after delivering the oil sand bitumen to the end user
with the oilfield
paying the "carrier rent and carrier loss fees". Since it is economically
unreasonable to sell
the diluting agent at a price lower than its original cost, the Oil Sand
Bitumen Company
generally uses the diluting agent provided by the Pipeline Company as the
carrier. The
diluting agents adopted by this process generally comprise light naphtha,
condensate or
synthetic crude oil (SCO), which is the product obtained by processing the oil
sand bitumen
by the delayed coking process. The amount of the diluting agent used is
approximately 66%
(by volume) of the oil sand bitumen. Use of a significant amount of high-value
diluting agent
would require enormous working capital and is economically unreasonable.
Furthermore, in
this process, the oil sand bitumen purchaser or the Oil Sand Bitumen Company
itself is
required to set up a distillation unit at the pipeline terminal and separate
the diluting agent for
recycling. However, it is difficult to effectively develop the oil sand
bitumen market because
of impediments for finding the right users that can meet the above-mentioned
conditions.
Additionally, transmit of the oil sand bitumen in admixture with the diluting
agent would in
itself increase the pipeline transmit load.
In addition, some oil sand bitumen companies apply the upgrading process
consisting of delayed coking as the main means to "convert heavy oils into
light ones" upon
processing the oil sand bitumen. The high-sulfur petroleum coke, a by-product
obtained by
said processing process, is sold at a much lower price and the distribution
thereof is difficult
owing to lack of buyers. It is well known that adoption of the technology for
hydroprocessing
the tower bottom heavy oil to reduce the sulfur content in petroleum coke
needs high
operating cost and is not beneficial for the investors.
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CN 1233644A discloses a "mild thermal cracking-solvent deasphalting"
combination process, which comprises feeding the straight-run heavy components
into a
thermal cracking reactor and mild thermal cracking them with a temperature of
380-450 C, a
pressure of 0-0.5 MPa and a residence time of 10-120 minutes; feeding the
resulted streams
after cracking reactions into a light ends separation unit to separate light
ends and heavy
components which is used as feed oil for the solvent deasphalting unit;
feeding a mixture of a
solvent which is one or more of selected from the group consisting of propane,
isobutene,
normal butane, and normal pentane and a feed oil for the solvent deasphalting
unit at a
volume ratio of 3-12:1 through a static mixer into a solvent deasphalting unit
followed by
two-stage or one-stage solvent deasphalting under the precritical or
supercritical conditions of
the solvent, with the solvent being reclaimed for recycling. This process is
aimed at
increasing the light distillate yield and improving the quality of the same.
CN 1485412A discloses a "solvent deasphalting-mild thermal cracking"
combination process, which comprises the following steps: separating the
feedstock in a
distillation unit to separate heavy components, feeding the heavy components
thus obtained
into the upper part of an extraction tower of the solvent deasphalting unit
while routing the
solvent into the lower part of the extraction tower at a predetermined ratio,
thereby the heavy
components and solvent enter into the extraction tower in countercurrent
contact extraction
with each other; sending the deasphalted oil (DAO) containing a large amount
of solvent back
for solvent recovery, while discharging the DOA containing a small amount of
solvent from
the bottom of extraction tower and then feeding the same into a visbreaking
unit, where the
DOA goes visbreaking reactions in a visbreaking reactor; and feeding the
streams exiting
from the visbreaker into a flash distillation tower to separate the visbreaker
gas, visbreaker
gasoline and visbreaker residuum. The main purpose of this method is to
enhance the linear
velocity of material streams in furnace tubes and extend the operating cycle
to find an outlet
for the gilsonite (hard bitumen) by reducing the energy assumption for solvent
recovery and
alleviating the coking of DOA inside the furnace tubes.
Although the above-mentioned prior arts has disclosed the methods for
processing
the heavy residuum through the combination method comprising mild thermal
cracking and
solvent deasphalting, the feedstocks adopted are heavy residuum and their
purposes are to
increase the light distillate yield and improve the product quality. As far as
the present
inventors know, it has not been disclosed that a method for processing oil
sand bitumen via a
combination method of mild thermal cracking and solvent deasphalting to
improve its
pipeline transmission performance and increase the economic benefits of the
oilfield.
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CA 02570231 2006-12-04
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the above disadvantages
existing
in the prior arts, i.e. high costs in pipeline transmission and processing of
the oil sand
bitumen, and to provide a low-cost method for processing and pipeline
transmitting oil sand
bitumen.
Another object of the present invention is to provide on the above-mentioned
basis a
method for processing the oil sand bitumen with better overall economic
benefits.
The present invention provides a method for processing oil sand bitumen, which
comprises the steps of visbreaking and solvent deasphalting the oil sand
bitumen to yield
DOA and components capable of being transmitted in pipeline.
The method for processing oil sand bitumen provided by this invention may
further
comprise a bitumen gasification step for gasifying obtained DOA upon contact
with oxygen
to generate steam and syngas. The syngas obtained from the bitumen
gasification can be
further used as the fuel for a steam-electricity cogeneration unit to generate
steam and
electricity necessary for the production operation at oilfield.
The method for processing oil sand bitumen provided by this invention can by
means of visbreaking and solvent deasphalting reduce the viscosity of bitumen
products and
effectively solve the problem concerning the pipeline transmission of the oil
sand bitumen.
The method provided by this invention is simple in operation, low in equipment
cost and
drastically low in operating cost, and not only can solve the problem
concerning high
investment required by purchasing massive diluting agent for the traditional
oil sand bitumen
processing unit, but also can remarkably reduce the high investment and
processing cost
required by the upgrading means mainly composed of the coking and
hydrogenation
processes. On the other hand, this invention can also by means of steam-
electricity
cogeneration technology convert the DOA mainly comprising heavy asphaltenes
and resins
into heat energy and electricity to provide a significant amount of steam and
power to save
massive natural gas necessary for steam generation at the oilfield, which is
especially of great
significance for the oilfield adopting the steam-aided gravitational drive
(SAGD) technology.
In the meantime, it is possible to reclaim a large amount of sulfur in the
sulfur recovery unit
(SRU), which is advantageous in solving the emission problem in compliance
with
environmental regulations.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a flow diagram showing one embodiment of processing oil sand bitumen
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CA 02570231 2006-12-04
provided by this invention
Fig. 2 is a flow diagram showing another embodiment of processing oil sand
bitumen provided by this invention
Fig. 3 is a flow diagram showing the process of DOA gasification provided by
this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method for processing oil sand bitumen provided by this invention
comprises
the steps of visbreaking and solvent deasphalting the oil sand bitumen to
yield DOA and
components capable of being transmitted in pipeline.
The oil sand bitumen described in this invention generally refers to the oil
sand
bitumen obtained through open pit mining or exploited through drilling coupled
with steam
heating followed by preliminary removing minerals such as sand and clay
contained therein.
The components capable of being transmitted in pipeline described in this
invention
refer to the materials that can be transmitted in pipeline at conventional
transmission
conditions in the crude oil transportation field. Preferably, said components
capable of being
transmitted in pipeline refer to the components having a viscosity less than
350 cSt at 8.
The term "visbreaking" mentioned in this invention refers to a mild thermal
cracking process and is mainly used to reduce the viscosity of the material
stream to the
maximum degree to improve the pipeline transmission performance of the oil
sand bitumen.
The viscosity reduction is achieved mainly through thermal cracking non-
asphaltenes.
Visbreaking is a matured oil refining process aimed at producing light
distillates from heavy
oil, and its process conditions are well known to the person skilled in the
art. The process
conditions of visbreaking used herein is not specially limited and said
visbreaking can be
carried out at different reasonable temperature and pressure conditions. It is
appreciated that
the person skilled in the art can easily find out suitable conditions to
achieve the objectives of
this invention in accordance with the technical solution of this invention.
The visbreaking
reactions described in the embodiments of this invention should be preferably
carried out
under the conditions of a temperature range of 350-500 , a pressure range of
0.3-15 MPa
and a residence time of 1-6 hours, and more preferably under the conditions of
a temperature
of 400-430 , a pressure of 2-10 MPa and a residence time of 2-4 hours.
The solvent deasphalting mentioned in this invention refers to a process of
separating the components contained in the oil sand bitumen according to the
rule of
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CA 02570231 2006-12-04
similarity between organic solvents and the components contained in oil sand
bitumen and is
a liquid-liquid extraction process, which can be carried out in various
vessels, preferably in
the extraction tower of solvent deasphalting unit in order to facilitate the
large scale
commercial production. After being processed in solvent deasphalting unit, the
oil sand
bitumen materials thus obtained are separated into two parts, one of which
dissolves in the
solvent and the other does not dissolve. Since the materials dissolved in the
solvent are
generally components with low molecular weight, they flow out from the tower
overhead
together with the solvent, known as the DAO, whereas the insoluble in the
solvent are heavy
components known as the DOA, and generally flow out from the deasphalting
tower bottom.
The DOA generally comprises heavy asphaltenes and resins.
The solvent used in the solvent deasphalting step in this invention is not
especially
limited and may be various organic solvents including the low-molecular
hydrocarbon
solvent such as one or more selected from the group consisting of propane, n-
butane,
isobutene, n-pentane, isopentane, n-hexane, cyclohexane, heptane and petroleum
ether,
preferably one or more of the hydrocarbons having 3-5 carbon atoms, namely
propane, n-
butane, isobutene, n-pentane and isopentane. Preferably, the solvent is used
in an amount of
3-12 and more preferably 4-10 (by volume) times of that of the feedstock. Said
solvent
deasphalting may be supercritical solvent deasphalting, precritical solvent
deasphalting or
conventional solvent deasphalting, and preferably the supercritical solvent
deasphalting
process, which is carried out under supercritical conditions. Said
supercritical conditions
comprise an operating temperature higher than the critical temperature of the
solvent and an
operating pressure higher than the critical pressure of the solvent, and the
critical values of
temperature and pressure may vary depending on the solvent. Within the range
of the above-
mentioned preferable solvents, the extraction temperature for supercritical
solvent
deasphalting is 10-200 , and the pressure is 0.2-10 MPa, and more preferably
the extraction
temperature is 140-180 and the pressure is 3-8 MPa.
In this invention, the oil sand bitumen may be subjected to solvent
deasphalting
followed by visbreaking, or may be subjected to the visbreaking followed by
solvent
deasphalting. Different operating sequences can have a slight influence on the
operating
conditions of each step, but both of them are realizable within the conditions
provided by this
invention.
According to one embodiment of this invention, the method for processing the
oil
sand bitumen includes visbreaking the oil sand bitumen and routing the
products thus
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CA 02570231 2006-12-04
obtained as the feedstock to the solvent deasphalting unit to yield DOA and
DAO. Whether
the solvent comprised therein is reclaimed or not, said DAO is used as the
components
capable of being transmitted in pipeline. In order to reduce the load of
visbreaker, said oil
sand bitumen is preferably routed into a distillation unit to separate the
components capable
of being transmitted in pipeline, and then the heavy components obtained in
the distillation
unit is subjected to deasphalting. Said distillation may be atmospheric
distillation and/or
vacuum distillation. The conditions of said distillation can be selected by
the ordinary person
skilled in the art according to the target fraction that needs to be
separated. The heavy
components mentioned herein are preferably the components boiling at 180 or
more.
Similarly, in order to reduce the load of solvent deasphalting unit, the
products obtained by
visbreaking is preferably routed into a light ends separation unit to separate
the components
capable of being transmitted in pipeline, and then the heavy components
obtained in the light
ends separation unit is subjected to solvent deasphalting. Said light ends
separation unit may
be various light ends separation units, for instance, an atmospheric
distillation tower, a
vacuum distillation tower or a flash distillation tower. The operation
conditions of said light
ends separation can be selected by the ordinary person skilled in the art
according to the
target fractions that need to be separated. The heavy components mentioned
herein are
preferably the components boiling at 180 or more, and more preferably the
components
boiling at 500 or more.
The above-mentioned embodiment can be realized through the process flow sheet
shown in Fig. 1(visbreaking-solvent deasphalting): the oil sand bitumen is
routed into a
distillation unit, in which the oil sand bitumen is separated into low-boiling
components as
the components capable of being transmitted in pipeline and heavy components,
and then the
high-boiling distillation residuum is routed into a visbreaking unit to be
visbroken under the
corresponding conditions with the visbreaking products being routed into the
light ends
separation unit to be separated into low-boiling components as the components
capable of
being transmitted in pipeline and high-boiling heavy components used as the
feedstock for
solvent deasphalting through contact extraction by means of the hydrocarbon
solvent in the
solvent deasphalting unit. After solvent deasphalting, the DAO containing a
significant
amount of solvent and the DOA with a small amount of solvent or without
solvent are
obtained, and the DAO is separated from the tower overhead to be used as the
components
for pipeline transmission, whether the solvent contained therein is reclaimed
or not. The
reclaimy of solvent from said DAO can be achieved by means of the known
methods, such as
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CA 02570231 2006-12-04
by means of distillation or gas-solid separation. Said DOA is discharged from
the tower
bottom.
In accordance with another embodiment of this invention, the method for
processing
oil sand bitumen provided by this invention includes the deasphalting of
bitumen from oil
sands to yield the DOA and the DAO and routing said DAO, whether the solvent
contained
therein is reclaimed or not, as the feedstock to the visbreaker to obtain the
components
capable of being transmitted in pipeline. In order to reduce the solvent
deasphalting load to
further save the cost, preferably the method provided by the present invention
comprises
separating the components capable of being transmitted in pipeline from the
oil sand bitumen
in the distillation unit and then solvent deasphalting the heavy components
obtained from the
distillation unit. Said heavy component mentioned herein preferably refers to
a fraction
boiling above at least 180 , and more preferably a fraction boiling above 500
. Said
distillation unit may include the atmospheric distillation unit and the vacuum
distillation unit.
In this embodiment, said oil sand bitumen is firstly separated in the
atmospheric distillation
unit into the overhead components capable of being transmitted in pipeline and
the tower
bottom atmospheric residuum (AR), and then the AR is routed into a vacuum
distillation unit
to be separated into vaccuum tower overhead oil and vacuum residuum, which is
solvent
deasphalted to yield the DOA and the DAO. Said DAO, whether the solvent
contained
therein is reclaimed or not, is commingled with the vacuum tower overhead oil
to serve as the
feedstock for visbreaking. Said DOA is discharged from the tower bottom.
The above-mentioned embodiment can be realized through the process flow sheet
shown in Fig. 2 (solvent deasphalting-visbreaking): The oil sand bitumen is
fed into the
atmospheric distillation section of the distillation unit, in which the low-
boiling components
contained in the oil sand bitumen are directly separated out as the components
capable of
being transmitted in pipeline, and the tower bottom AR is fed into the vacuum
distillation
section of the distillation unit to be separated into the vacuum tower
overhead oil and vacuum
residuum. Said vacuum residuum is in contact with a hydrocarbon solvent to be
subjected to
contact extraction in solvent deasphalting unit. After solvent deasphalting,
the DAO
containing a significant amount of solvent and the DOA with a small amount of
solvent or
without solvent are obtained. And the DAO is separated from the tower overhead
and
whether the solvent contained therein is reclaimed or not, the DAO is
commingled with said
vacuum tower overhead oil,and fed into the visbreaking unit to be subjected to
visbreaking
under the conditions of visbreaking. The products of visbreaking are used as
the components
capable of bing transmitted in pipeline. The recovery of solvent from said DAO
can be
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CA 02570231 2006-12-04
achieved by means of the known methods, such as by means of distillation or
gas-solid
separation. Said DOA is discharged from the tower bottom.
As shown in Fig.l and Fig. 2, the above-mentioned method for processing the
oil
sand bitumen may also include separating the gaseous components from those
components
capable of being transmitted in pipeline and delivering them to the oilfield
fuel system to be
used as fuel or to be marketed.
In the prior art, the DOA obtained by solvent deasphalting is directly used as
the
starting material for making the road asphalt. The present inventor has
discovered that
gasification of the DOA upon contact with an oxidative gas can produce a large
amount of
heat for steam generation, which is exactly needed by the petroleum
exploitation industry,
and can also produce a significant amount of syngas, such as carbon monoxide
and hydrogen
and the like. The syngas thus obtained can be used as the fuel for a steam-
electricity
cogeneration unit to generate the steam and electricity much needed by the
oilfield
production activities. Therefore, the method for processing the oil sand
bitumen provided by
this invention also preferably includes the step for gasification of the DOA.
The process flow
sheet of said gasification step is shown in Fig. 3, wherein the DOA feedstock
is in contact
with an oxidative gas in the bitumen gasification unit to undergo non-complete
oxidation
reactions at a temperature of 200-1500 and a pressure of 2.0-10.0 MPa to yield
the syngas.
Said oxidative gas may be oxygen or air. Since the syngas produced by this
method
comprises significant amount of sulfur and metal elements derived from the oil
sand bitumen,
the method provided by this invention also preferably includes the step for
recovery of sulfur.
Said sulfur recovery step is carried out in the sulfur recovery unit (SRU).
The syngas after
reclamation of sulfur and metals contained therein becomes a purified gas and
can be directly
used as the feedstock of the cogeneration unit. As a result, no only a sizable
amount of sulfur
can be produced as a by-product, but also the environmental pollution caused
by combustion
of sulfur comprised in the syngas can be alleviated. The sulfur reclaimed
thereby can be
processed into solid sulfur, liquid sulfur, sulfuric acid and other sulfur
products. Accordingly,
said method for processing oil sand bitumen provided by this invention also
preferably
comprises the steam-electricity cogeneration step, and the fuel of which is
the syngas formed
during bitumen gasification. Said steam-electricity cogeneration unit is a
unit that can
generate steam and electricity at the same time and also represents a matured
technique,
which usually uses the syngas as the fuel with the ratio of steam and
electricity generated
being adjustable depending on the demand. For example, said steam-electricity
cogeneration
unit includes but is not limited to the corresponding facilities and equipment
made by the GE
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CA 02570231 2006-12-04
Company. Said sulfur recovery can be, for instance, realized through scrubbing
syngas
followed by using relevant technical for sulfur recovery.
On one hand, the method for processing the oil sand bitumen provided by the
present invention can solve the problem concerning the pipeline transmission
of oil sand
bitumen by reducing the viscosity of bitumen products via solvent deasphalting
and
visbreaking and separating and pipeline transmitting the light components from
oil sand
bitumen as the components capable of being transmitted in pipeline. On the
other hand, the
method for processing oil sand bitumen provided by this invention can also
bring about
optimal overall economic benefits, which are especially important for the
oilfield using the
SAGD technology, via gasification and purification the DOA that is rich in
heavy asphaltenes
and resins by gasification step and routing the resulted purified syngas to a
steam-electricity
regeneration unit as the fuel and converting the DOA into heat and electrical
energy on the
spot to provide a significant amount of steam and electricity to meet the
oilfield production
needs, which can save an enormous amount of natural gas which would be
purchased for
steam generation along with savings in expenses for the DOA transportation,
Meanwhile, a
large amount of sulfur can be reclaimed after cleanup operation in the SRU,
which is
advantageous in solving the emission problems. By the above-mentioned
processing method,
all components contained in the oil sand bitumen feedstock can play their
roles to the
maximum extent and thus significantly improve the utilization and economic
benefits of the
oil sand bitumen. Furthermore, the process provided by this invention is
advantageous of
simple operation, low equipment cost and greatly reduced operating cost, which
not only can
solve the problem associated with large investment in purchase of the diluting
agent needed
by the traditional unit for processing the oil sand bitumen, but also can
reduce the high
investment cost and high processing cost of the upgrading method based on the
main avenues
of coking and hydrogenation processes.
The present invention will be detailed illustrated by the following examples,
which
is just for purpose of illustration but not any limit to the present
invention. The oil sand
bitumen used in the following examples is the oil sand bitumen excavated in a
preheated state
produced at a company with its major properties presented in the following
Table 1, while
butane and pentane are obtained from the commercial units. The extraction
tower for solvent
deasphalting is a medium-size solvent deasphalting unit with a capacity of 10
kg/h, and the
capacity of the visbreaker is 10 kg/h, and bitumen gasification unit is a
gasification unit
licensed by GE, whereas SRU is used to reclaim the sulfur.
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EXAMPLE I
According to the process shown in Fig. 1, the oil sand bitumen is routed to
the
distillation unit to directly separate the components boiling below 200 as the
components
capable of being transmitted in pipeline from the oil sand bitumen, with the
remaining high-
boiling point distillation residue entering the visbreaking unit to be
subjected to visbreaking
at a temperature of 400 , a pressure of 0.5 MPa and a residence time of 2
hours. The
visbreaking products are routed to the light ends separation unit, where the
visbreaking
products are separated into the components boiling below 500 as the components
capable
of being transmitted in pipeline and the remaining high-boiling point heavy
components used
as the feedstock of the solvent deasphalting. Said heavy components is carried
out the contact
extraction with n-butane solvent in the solvent deasphalting unit under the
following
conditions: a tower bottom temperature of 140 , a tower overhead temperature
of 160 , a
pressure of 6 MPa, and a ratio between n-butane and the feedstock i.e. high
boiling point
heavy components of 4:1. After solvent deasphalting, the DAO containing a
significant
amount of solvent and the DOA with or without a slight amount of solvent are
obtained. The
DAO is separated from the tower overhead and can be used as the components
capable of
being transmitted in pipeline after reclamation of the solvent. The components
capable of
being transmitted in pipeline obtained in all the above-mentioned processing
steps are
gathered and combined, from which samples are taken for analysis to determine
the viscosity,
density and boiling point thereof. The results are presented in the following
Table 1. Said
DOA is discharged from the tower bottom and used as the feedstock to the
cogeneration unit
of steam and electricity after being subjected to gasification and sulfur
removal.
EXAMPLE 2
According to the process shown in Fig. 2, the oil sand bitumen is routed to
the
atmospheric distillation unit to directly separates the tower overhead
components boiling
below 200 as the components capable of being transmitted in pipeline from the
oil sand
bitumen, with the AR from the tower bottom being routed to the vacuum
distillation unit and
being separated into the tower overhead oil boiling between 200-500 and the
vacuum
residuum (VR) boiling above 500 . Said VR is subjected to contact extraction
with the
pentane mixed solvent in the solvent extraction unit under the following
conditions: a tower
bottom temperature of 150 , a tower overhead temperature of 170 , a pressure
of 5 MPa,
and a solvent ratio of 4:1. After the step of solvent deasphalting, a DAO
comprising a large
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CA 02570231 2006-12-04
amount of solvent and a DOA comprising little or a little of solvent are
obtained. The DAO is
separated from the tower overhead and is combined after solvent recovery with
said vacuum
tower overhead oil and then both are routed into the visbreaking unit to
visbreaking under the
following conditions: a temperature of 430 , a pressure of 2 MPa, and a
residence time of 3
hours. The visbreaker products are used as the components capable of being
transmitted in
pipeline. The components capable of being transmitted in pipeline obtained in
all the above-
mentioned processing steps are gathered and combined, from which samples are
taken for
analysis to determine the viscosity, density and boiling point thereof. The
results are shown in
the following Table 1. Said DOA is discharged from the tower bottom and used
as the
feedstock to the cogeneration unit of steam and electricity after gasification
sulfur removal.
Table 1
Feedstock Product
example Density Viscosity (cSt) Components capable of being transmitted in
pipeline
number Density Distillation range
g/cm3 (at 25 ) g/cm () Viscosity (cSt) (at 8
cm
Example 1 1.018 400000 0.98 650 300
Example 2 1.018 421400 0.99 650 310
It can be seen from the above Table I that, via the solvent deasphalting and
visbreaking steps, the method for processing the oil sand bitumen provided by
the present
invention can significantly reduce the viscosity of the bitumen products and
make the non-
asphaltene fraction separated from the oil sand bitumen as the components
capable of being
transmitted in pipeline and thus effectively solves the problem concerning
pipeline
transmission of the oil sand bitumen.
12
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