Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ENDOGENOUS ASPHALTENIC ENCAPSULATION OF BITUMINOUS
MATERIALS WITH RECOVERY OF LIGHT ENDS
FIELD OF THE INVENTION
[0001] The invention is in the field of methods for shaping materials, in
particular
by physically and chemically treating viscous bituminous liquids to form
discrete
solid-encapsulated shapes, optionally with associated recovery of light ends
as a
separate product stream.
BACKGROUND OF THE INVENTION
[0002] It is common practice to segregate petroleum substances of high
viscosity
and density into two categories, "heavy oil" and "bitumen". For example, some
sources define "heavy oil" as a petroleum that has a mass density of between
about
920 kg/m3 (or an API gravity of about 26 ) and 1,000 kg/m3 (or an API gravity
of
about 10 ). Bitumen is sometimes described as that portion of petroleum that
exists
in the semi-solid or solid phase in natural deposits, with a mass density
greater than
about 1,000 kg/m3 (or an API gravity of about 10 ) and a viscosity greater
than
10,000 centipoise (cP or 10 Pa.$) measured at original temperature in the
deposit
and atmospheric pressure, on a gas-free basis. Although these terms are in
common use, references to heavy oil and bitumen represent categories of
convenience, and there is a continuum of properties between heavy oil and
bitumen.
Accordingly, references to heavy oil and/or bitumen herein include the
continuum of
such substances, and do not imply the existence of some fixed and universally
recognized boundary between the two substances. In particular, the term "heavy
oil"
includes within its scope all "bitumen" including hydrocarbons that are
present in
semi-solid or solid form. Similarly, a "bituminous" material is one that
includes a
bitumen component, as that component is broadly defined.
[0003] Bituminous liquids generally include an asphaltene component.
Asphaltenes may for example be suspended as a nanocolloid or otherwise
dispersed within a bituminous liquid. Asphaltenes may be defined practically
by
differential solubility, for example as the component of a bituminous material
that is
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insoluble in n-alkanes, such as n-pentane or n-heptane, and soluble in toluene
or
benzene. In molecular terms, asphaltenes are generally present as a complex
mixture that includes high molecular weight polyaromatic carbon ring units,
with
oxygen, nitrogen, and sulfur heteroatoms, as well as alkane chains and cyclic
alkanes. As used herein, the term "asphaltenes" encompasses this wide range of
variously defined materials, and an "asphaltenic" material is one that
includes an
asphaltene component, as that component is broadly defined.
[0004] The presence of asphaltenes in bitumen has in some circumstances
been
suggested to represent a potential production or transportation problem.
During
production, for example, asphaltene precipitation and deposition are
recognized
risks that may result from changes in pressure, temperature, chemical
composition
and shear rate. In contrast, in some bitumens, relatively high asphaltene
concentrations appear to be present as a stable viscoelastic network (Yang and
Czarnecki, 2005, Energy & Fuels 19, no. 6: 2455-2459). In the context of
transportation, methods have for example been described for removing
asphaltenes
from bitumen prior to transport (see for example US Patent Publication
20170002275). For these and other reasons, a wide range of processes are known
for removing asphaltenes from petroleum liquids, for example in de-asphalter
units in
crude oil refineries or bitumen upgraders, such as solvent de-asphalter units
that
separate the asphaltenes by virtue of the fact that light hydrocarbons, such
as
propane, butane or pentane, will dissolve aliphatic compounds but not
asphaltenes.
[0005] Heavy oils and bitumen can be separated into not only viscous
components such as asphaltenes but also lighter materials. These light ends
are
composed of saturate (alkane) and aromatic components and typically have
viscosities lower than that of the asphaltenic component. Upon heating of
heavy oil
or bitumen, reactions occur that can break bonds in the heavy components of
the
heavy oil and bitumen leading to the generation of lighter materials such as
saturate
and aromatic components. These components, when mixed with the original heavy
oil and bitumen, can lead to an upgraded oil product.
[0006] The foregoing characteristics of heavy oils and bitumen give rise to
a
variety of risks and challenges associated with transportation, handling and
storage,
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in liquid form or otherwise. There is accordingly an ongoing need for improved
techniques for transporting and handling heavy oil and bitumen. Furthermore,
if the
heavy oil or bitumen is processed for transportation which generates lighter
components from the reactions done to prepare the heavy oil or bitumen for
transport, then these light components can be collected and sold as a product
stream or collected and remixed with the original heavy oil and bitumen to
yield the
original oil product or a partially upgraded oil product.
SUMMARY
[0007] In one aspect of the invention, processes are provided that take
advantage of the recognition that endogenous asphaltenes in a bituminous
liquid
may be induced to coalesce on the surface of an aliquot of the bituminous
liquid, so
as to form a resilient membrane that has sufficient structural integrity to
retain the
remaining bituminous liquid in the form of a discrete shape. In effect,
endogenous
asphaltenes in the bituminous liquid are converted into a resilient solidified
surface
layer on shaped units of the bituminous liquid. These pellets or capsules of
bitumen
are then amenable to material handling techniques adapted for particulate
solids.
During these processes to form endogenous asphaltenes on the surface of an
aliquot of the bituminous liquid, light components may be generated from
reactions
that occur at the surface of the bituminous liquid. These light components are
generally composed of relatively low molecular weight alkanes (linear
hydrocarbons
up to C20 alkanes and potentially above) and aromatics (cyclic hydrocarbons up
to
C20 aromatics and potentially above). These light components can be collected
as
a separate liquid product stream.
[0008] Methods are accordingly provided for segregating a bituminous liquid
into
discrete shaped units. In a continuous process, generally applied to heated
bitumen,
the bituminous liquid may be divided into shaped liquid aliquots, each aliquot
having
a discrete shape defined by a material handing mechanism that contains the
aliquot.
For example, in a process analogous to gravure printing, a rotating cylinder
may be
shaped with indentations, and the surface of the cylinder flooded with
bituminous
liquid. The cylinder may then be wiped with a doctor blade, so that separate
aliquots
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of the bituminous liquid remain within each of the recessed indentations. The
exterior surface of each shaped aliquot may then be treated, for example by
heating
of the rotating cylinder, so that the indented gravure cylinder acts as a
heated
coating roll, with the heat forming an outer membrane of asphaltenic material
from
the shaped bituminous liquid. In this way, each shaped aliquot is encapsulated
within a resilient asphaltenic coating. The outer asphaltenic layer is
sufficiently
resilient to retain the discrete shape of the shaped aliquot when the aliquot
is
released from the material handling mechanism. In a process again analogous to
the
transfer of ink in gravure printing, the shaped aliquots may for example be
released
from the patterned rotating cylinder onto a substrate, for example after being
nipped
between a second heated backing roll and the heated patterned gravure roll.
The
shaped aliquots released onto the substrate form resiliently shaped units of
bituminous liquid encapsulated in the asphaltenic outer membrane, which may
for
example be cooled on the substrate, and then released from the substrate, for
example with a scraper, producing pellets of bituminous liquid. During the
process
analogous to gravure printing, the light components generated during the step
of
forming the shaped bituminous liquid can be collected into a separate liquid
product
stream.
[0009] In alternative aspects, the density of the units of bituminous
liquid
produced by processes of the invention may be adjusted, for example by
incorporating agents within the pellets such as gas bubbles, catalysts, or
solvents. In
some embodiments, pellets can accordingly be designed to be buoyant in water,
which may for example facilitate recovery of the pelleted material in the
event of an
environmental release or spill.
[0010] In other alternative aspects, the light component stream may be
collected
and sold as an individual product or can be mixed at a later time with the
units of
bituminous liquid to form a mixture similar to the original heavy oil or
bitumen or a
partially upgraded oil.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram exemplifying one implementation of the methods
described herein for treating a heavy oil or bitumen to a pelletized form and
recover
the light components formed during the process.
[0012] FIG. 2 is a diagram exemplifying another implementation of the
methods
described herein for treating a heavy oil or bitumen to a pelletized form and
recover
the light components formed during the process.
[0013] FIG. 3 is a diagram exemplifying another implementation of the
methods
described herein for treating a heavy oil or bitumen to a pelletized form and
recover
the light components formed during the process.
[0014] FIG. 4 is a diagram exemplifying another implementation of the
methods
described herein for treating a heavy oil or bitumen to a pelletized form and
recover
the light components formed during the process.
[0015] FIG. 5 is a diagram illustrating different pellet shapes obtained
from a
patterned roll to convert heavy oil or bitumen to a pelletized form.
[0016] FIG. 6 includes three photographic images, illustrating
characteristics of
raw bitumen, spherical pellets and a vapor condensate.
[0017] FIG. 7 is a table listing properties of original bitumen, the skin
encapsulating spherical pellets and the bitumen or heavy oil product after
extraction
from an encapsulated pellet.
[0018] FIG. 8 is a diagram illustrating an alternative embodiment of the
invention.
[0019] FIG. 9 includes two images illustrating a cylindrical bitumen pellet
and
draining of the encapsulated bitumen within the pellet.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Methods are provided to pelletize a wide variety of heavy oils and
bitumen, including for example residual oil fractions from upgrading and
refining
plants with simultaneous collection of lighter components into a separate
product
stream. In some implementations, continuous high speed methods are provided,
as
illustrated in Figures 1-6. Units or pellets of bituminous material may be
produced of
widely variable size and density.
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[0021] In select methods, a heated gravure patterned roll apparatus is
employed
within a controlled material handling environment, to convert a heavy oil or
bitumen
stream into separate small units of specific shape. The patterned roll may be
used
to apply heat to the exterior of the pellets. The output from the gravure roll
apparatus
may be a pelletized form of heavy oil or bitumen that has a relatively thin
semi-solid
or solid coating on the surface that is sufficiently resilient to contain a
liquid heavy oil
or bitumen within the pellet and lighter components into a separate product
stream.
In alternative embodiments, the patterned roll may be shaped so as to provide
pellets of widely variable shape, such as spheres, ellipsoids, cubes,
pyramids,
double pyramids, or other shapes. FIG. 5 displays example patterns that can be
used to form the bitumen pellets. In select embodiments, the dimensions of the
pellets can for example range from millimeters to tens of centimeters, with
some
preferred size embodiments being on the order of a few centimeters.
[0022] FIG. 1 illustrates an implementation of the present methods for
treating a
heavy oil or bitumen with simultaneous collection of lighter components into a
separate product stream. In this method, the bitumen is heated and flows into
a
tank. The heating is carried out so that the viscosity of the heavy oil or
bitumen
drops to facilitate processing with the patterned roll apparatus. In select
embodiments, the temperature range for this heating may for example be between
about 150 C and 250 C. In select embodiments, at this stage, the temperature
may
be constrained to under about 250 C, to minimize reactions from occurring in
the
heavy oil or bitumen. The heat can for example be delivered through a variety
of
methods, including heat tracing tape, steam heating, and electrical heating.
The
light components can be collected by using a cool surface or a standard
condensation coil.
[0023] As illustrated in Fig. 1, a patterned roll dips into the tank and
the patterns
in the roll are filled with hot bitumen. The heated patterned roll may for
example be
maintained at between about 300 C and 500 C, most preferably between 350 C and
450 C.
[0024] The surface of the patterned roll may for example be constructed of
a
oleicophobic material. The bitumen in the recessed patterns on the roll may
then be
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deposited on a oleicophobic substrate, which as illustrated is heated by a
backing
roll. The bitumen patterns on the substrate are then cooled and scraped off
the
substrate for subsequent transport or processing. The mechanism may be adapted
so that reactions on the outer surface of the bitumen pellet occur in the nib,
the
contact region between the rolls, to form the exterior coating on the pellet.
The rolls
can for example be loaded, so that there exists a positive pressure in the
nib. In this
way, the heat and pressure of patterned roll and nib cause reactions that lead
to the
formation of a thin solid layer on the surface of the bitumen pellet. For
example,
thermal cracking (pyrolysis) reactions may occur which produce a viscous
coating on
the surface of the pellets, and asphaltene precipitation may also occur in a
way
which helps to strengthen the coating on the surface of the pellet.
[0025] The controlled material handling environment may for example include
mechanisms for applying additional surface treatments to the pellets, for
example by
treating the exterior of the pellets with chemical agents and/or ultrasonic
stimulation.
These additional surface treatments may for example be applied so as to
improve a
desired quality of the outer coating. For example, aliquots of bituminous
liquid may
be exposed to chemical agents such as CO2, propane, pentane or heptane. In
addition, physical treatments in addition to heating may be applied, such as
ultrasound. To form the coating on the outside of the heavy oil or bitumen
pellets,
the chemical changes that occur on the outside of the heavy oil or bitumen
pellet
may for example include asphaltene precipitation and thermal cracking
(pyrolysis -
splitting larger hydrocarbon chains into smaller-chained compounds). In
particular, in
the nib of the patterned roll system, a solvent may be introduced to increase
the
formation of asphaltene on the surface of the pellets.
[0026] At the downstream side of the unit, the light components are
collected by
using a condenser. The liquid condensate is collected and removed as a product
stream. The condenser can take any form including a chilled plate or a
standard
condenser coil.
[0027] FIG. 2 illustrates an exemplary embodiment in which a solvent zone
is
placed just up-stream of the nib with simultaneous collection of lighter
components
into a separate product stream. Process conditions may be selected in such an
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embodiment so as to cause further asphaltene precipitation from the bitumen at
the
surfaces of the bitumen pellets. Alternative solvents include propane,
pentane, and
heptane.
[0028] FIG. 3 shows another exemplary embodiment, in which ultrasonic
stimulation is used in the nib with simultaneous collection of lighter
components into
a separate product stream. Process conditions may be selected in such an
embodiment so as to further cause the precipitation of asphaltenes on the
outer
surface of the bitumen pellet, as the aliquot of bituminous liquid is retained
in the
pattern. Ultrasonic stimulation may for example be carried out so as to cause
sonochemical reactions to occur, for example reactions that lead to
viscosification of
the bitumen. In select embodiments, the frequency of operation of the
ultrasonic
stimulation may for example be between about 20 and 40 kHz.
[0029] FIG. 4 illustrates an embodiment in which heat, solvent, and
ultrasonic
stimulation are all used to form the skin on the surface of the bitumen pellet
with
simultaneous collection of lighter components into a separate product stream.
In
further alternatives, other fluid distribution systems can be used, such as a
slot
coater, to place the bitumen on the patterned roll.
[0030] As illustrated in Figs. 1-4, in select embodiments, downstream of
the
pattern roll apparatus, the pellets may be cooled, for example to ambient or
chilled
conditions. In this way, after the pellets emerge from the nib, the pellets
are cooled
so as to facilitate separation of the pellets from the backing web
(substrate). Chilling
is also contemplated, to collect lighter components into a separate product
stream.
[0031] In some embodiments, prior to the patterned roll apparatus, the
heavy oil
or bitumen may be mixed with other materials to yield a pellet with other
functional
capabilities. For example, the oil can be partially foamed so that it has a
gas within
the liquid which alters the overall density of the oil yielding pellets that
float on water.
For example, as illustrated in Fig. 1, the bitumen can be foamed before it
enters the
tank so that it forms a foamed bitumen pellet. The gas used to create the foam
can
for example be nitrogen or carbon dioxide. The amount of gas in the pellets
can be
controlled to control the overall density of the bitumen pellets. In another
implementation of the method, encapsulated solvent can be added to the heavy
oil
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or bitumen yielding a pellet that contains solvent which when the pellet is
processed
can be used as part of the product. Similarly, in a further alternative
implementation,
one or more catalysts can be distributed within the heavy oil or bitumen
pellets, for
example to facilitate future processing of the bituminous liquid.
[0032] In alternative embodiments, the processing time and conditions in
the
patterned roll apparatus can be altered to provide a thicker coating on the
pellets. In
this manner, the overall chemical composition of the pellet can be tuned to a
specific
need. For example, the asphaltene content can be raised so that the pellets
are
more amenable for asphalt processing for road construction.
[0033] FIG. 6 shows an example of bitumen pellets created by using one of
the
methods described herein. The first image of FIG. 6 displays the raw bitumen.
The
second image of FIG. 6 displays the bitumen pellets. The thickness of the skin
is
less than 1 mm. The third image of FIG. 6 shows the liquid condensate formed
from
the process. The density of the liquid condensate is equal to 0.875 g/cm3.
[0034] FIG. 7 sets out data from analysis of the interior bitumen and
external skin
of an exemplary bitumen pellet. The original bitumen is a liquid with
viscosity of
about 1 million cP. After the process, the outer skin is a solid and has a
Young's
modulus equal to 0.1 GPa. The asphaltene content of the original bitumen and
skin
are 18 and 35 weight percent, respectively. The encapsulated bitumen within
the
pellet has essentially the same properties as that of the original bitumen.
The data
shows that the skin is relatively thin and rigid.
[0035] FIG. 8 illustrates a further alternative implementation of the
methods of the
invention, in which droplets of bitumen are formed in a solvent bath to form a
asphaltenic skin on the outer surface. These methods may for example produce
spherical or nearly spherical bitumen pellets.
[0036] FIG. 9 shows an example of a bitumen pellet created by using one of
the
methods described herein. The first image of FIG. 9 displays a cylindrical
bitumen
pellet. The second image of FIG. 9 displays the bitumen draining from the
pellet
after it was opened and heated. The viscous bitumen drains from the pellet.
The
thickness of the skin is less than 1 mm.
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[0037] In alternative implementations of the methods described herein, the
bitumen pellets can be coated, for example with solid asphaltene or coke or
polymers. This coating may for example be applied so as to reinforce the
mechanical properties of the pellets.
[0038] In another implementation, during the formation of the skin on the
pellet,
light ends from the heavy oil or bitumen may be released and subsequently
captured
as a separate product stream. The methods of capture may for example involve
containing the downstream side of the pelletization unit within an enclosure
where
the released vapour light ends are collected in a condenser or chilled
condenser or
collected on a cool surface and then directed into a collection system for
further
processing.
[0039] In a further step, the light ends may be recombined with the bitumen
pellets to form a new heavy oil or bitumen mixture. This may for example be
done
by using methods to crush and mix liquids and solids such as a crusher or
screw
extruder or similar device.
[0040] Although various embodiments of the invention are disclosed herein,
many adaptations and modifications may be made within the scope of the
invention
in accordance with the common general knowledge of those skilled in this art.
Such
modifications include the substitution of known equivalents for any aspect of
the
invention in order to achieve the same result in substantially the same way.
Numeric
ranges are inclusive of the numbers defining the range. The word "comprising"
is
used herein as an open-ended term, substantially equivalent to the phrase
"including, but not limited to", and the word "comprises" has a corresponding
meaning. As used herein, the singular forms "a", "an" and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for example,
reference
to "a thing" includes more than one such thing. Citation of references herein
is not
an admission that such references are prior art to the present invention. Any
priority
document(s) and all publications, including but not limited to patents and
patent
applications, cited in this specification are incorporated herein by reference
as if
each individual publication were specifically and individually indicated to be
incorporated by reference herein and as though fully set forth herein. The
invention
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includes all embodiments and variations substantially as hereinbefore
described and
with reference to the examples and drawings.
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