Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
UPGRADING A HEAVY HYDROCARBON FEEDSTOCK AND PRODUCING A
PITCH FRACTION
BACKGROUND
Field of Disclosure
[0001] The disclosure relates generally to the field of oil sand
processing, and more
particularly to heavy hydrocarbon feedstock upgrading.
Description of Related Art
[0002] This section is intended to introduce various aspects of the
art, which may be
associated with the present disclosure. This discussion is believed to assist
in providing a
framework to facilitate a better understanding of particular aspects of the
present disclosure.
Accordingly, it should be understood that this section should be read in this
light, and not
necessarily as admissions of prior art.
[0003] Modern society is greatly dependent on the use of hydrocarbon
resources for
fuels and chemical feedstocks. Hydrocarbons are generally found in subsurface
formations
that can be termed "reservoirs". Removing hydrocarbons from the reservoirs
depends on
numerous physical properties of the subsurface formations, such as the
permeability of the
rock containing the hydrocarbons, the ability of the hydrocarbons to flow
through the
subsurface formations, and the proportion of hydrocarbons present, among other
things. Easily
harvested sources of hydrocarbons are dwindling, leaving less accessible
sources to satisfy
future energy needs. As the costs of hydrocarbons increase, the less
accessible sources become
more economically attractive.
[0004] Recently, the harvesting of oil sand to remove heavy oil has become
more
economical. Hydrocarbon removal from oil sand may be performed by several
techniques.
For example, a well can be drilled to an oil sand reservoir and steam, hot
air, solvents, or a
combination thereof, can be injected to release the hydrocarbons. The released
hydrocarbons
may be collected by wells and brought to the surface. In another technique,
strip or surface
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mining may be performed to access the oil sand, which can be treated with
water, steam or
solvents to extract the heavy oil.
[0005] Oil sand extraction processes are used to liberate and
separate bitumen from
oil sand so that the bitumen can be further processed to produce synthetic
crude oil or mixed
with diluent to form "dilbit" and be transported to a refinery plant. Numerous
oil sand
extraction processes have been developed and commercialized, many of which
involve the
use of water as a processing medium. Where the oil sand is treated with water,
the technique
may be referred to as water-based extraction (WBE) or as a water-based oil
sand extraction
process. WBE is a commonly used process to extract bitumen from mined oil
sand.
[0006] One WBE process is the Clark hot water extraction process (the
"Clark
Process"). This process typically requires that mined oil sand be conditioned
for extraction by
being crushed to a desired lump size and then combined with hot water and
perhaps other
agents to form a conditioned slurry of water and crushed oil sand. In the
Clark Process, an
amount of sodium hydroxide (caustic) may be added to the slurry to increase
the slurry pH,
which enhances the liberation and separation of bitumen from the oil sand.
Other WBE
processes may use other temperatures and may include other conditioning
agents, which are
added to the oil sand slurry, or may operate without conditioning agents. This
slurry is first
processed in a Primary Separation Cell (PSC), also known as a Primary
Separation Vessel
(PSV), to extract the bitumen from the slurry.
[0007] In one WBE process, a water and oil sand slurry is separated into
three major
streams in the PSC: bitumen froth, middlings, and a PSC underflow (also
referred to as coarse
sand tailings (CST)).
[0008] Regardless of the type of WBE process employed, the process
will typically
result in the production of a bitumen froth that requires treatment with a
solvent. For example,
in the Clark Process, a bitumen froth stream comprises bitumen, solids, and
water. Certain
processes use naphtha to dilute bitumen froth before separating the product
bitumen by
centrifugation. These processes are called naphtha froth treatment (NFT)
processes. Other
processes use a paraffinic solvent, and are called paraffinic froth treatment
(PFT) processes,
to produce pipelineable bitumen with low levels of solids and water. In the
PFT process, a
paraffinic solvent is used to dilute the froth before separating the product,
diluted bitumen, by
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gravity. A portion of the asphaltenes in the bitumen is also rejected by
design in the PFT
process and this rejection is used to achieve reduced solids and water levels.
In both the NFT
and the PFT processes, the diluted tailings (comprising water, solids and some
hydrocarbon)
are separated from the diluted product bitumen.
[0009] Solvent is typically recovered from the diluted product bitumen
component
before the bitumen is delivered to a refining facility for further processing.
[0010] The PFT process may comprise at least three units: Froth
Separation Unit
(FSU), Solvent Recovery Unit (SRU) and Tailings Solvent Recovery Unit (TSRU).
Mixing
of the solvent with the feed bitumen froth may be carried out counter-
currently in two stages
in separate froth separation units. The bitumen froth comprises bitumen,
water, and solids. A
typical composition of bitumen froth is about 60 wt. % bitumen, 30 wt. %
water, and 10 wt.
% solids. The paraffinic solvent is used to dilute the froth before separating
the product
bitumen by gravity. The foregoing is only an example of a PFT process and the
values are
provided by way of example only. An example of a PFT process is described in
Canadian
Patent No. 2,587,166 to Sury.
[0011] From the PSC, the middlings, which may comprise bitumen and
about 10-30
wt. % solids, or about 20-25 wt. % solids, based on the total wt. % of the
middlings, is
withdrawn and sent to the flotation cells to further recover bitumen. The
middlings are
processed by bubbling air through the slurry and creating a bitumen froth,
which is recycled
back to the PSC. Flotation tailings (FT) from the flotation cells, comprising
mostly solids and
water, are sent for further treatment or disposed in an external tailings area
(ETA).
[0012] Oil sands bitumen, produced in Western Canada, is extremely
viscous
(viscosity >100,000 cSt) and requires blending with a substantial amount of
diluent (25-40
volume %) to meet pipeline viscosity specification. Diluent addition
represents a significant
cost to bitumen producers. Due to the significant cost of diluent, as well as
the bitumen/diluent
(dilbit) blend's quality debit, partial upgrading of bitumen is desirable.
[0013] By definition, 'full' bitumen upgrading entails converting
bitumen (via thermal
or catalytic process, such as coking, hydrocracking, fluid catalytic cracking
(FCC), etc.) into
synthetic crude oil (SCO), which contains no resid (1050T+) boiling range
molecules.
'Partial' upgrading, on the other hand, is defined as any combination of
processing steps to
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convert bitumen/heavy oil to an oil product with sufficient fluidity to enable
pipeline transport
with significantly reduced (or no) diluent addition.
[0014] Table 1 provides pipeline specifications to transport crude
oil from Alberta.
Table 1 ¨ Pipeline specifications to transport crude oil from Alberta
Property Specification
Viscosity < 350 cSt at pipeline temp
Density, kg/m3 < 940
Gravity API > 19
Base sediment & water <0.5 vol%
Olefin content <1 wt%
[0015] Bitumen has an extremely low H/C ratio and can have up to 50%
resid
(1050F+) fraction. Carbon rejection methods (e.g. coking, deasphalting) are
proven for
upgrading, but come with challenges (e.g. lower liquid yields). Hydrogen
addition methods
(e.g. fixed-bed hydro-processing, slurry hydrocracking), on the other hand,
increase yields but
are expensive and require H2 production and sulfur management facilities.
These ancillary
processes can cause upgrading to be economically infeasible (due to higher
capital).
Therefore, while full/partial upgrading provides significant quality uplift
and produces a lower
viscosity and density crude oil, the costs association with building an
upgrader may be high
or prohibitive. Thus, there remains a need for alternative methods of
upgrading bitumen.
SUMMARY
[0016] A disclosed method comprises providing a heavy hydrocarbon
feedstock
comprising paraffinic froth treated bitumen and/or solvent de-asphalted
bitumen; thermally
cracking the heavy hydrocarbon feedstock to produce a cracked stream and a
gas; distilling
the cracked stream to produce (i) a distillation bottoms stream and (ii) a
naphtha and distillates
stream; and de-asphalting the distillation bottoms stream to produce a pitch
fraction and
de-asphalted oil (DAO).
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[0017] The foregoing has broadly outlined the features of the present
disclosure so
that the detailed description that follows may be better understood.
Additional features will
also be described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] These and other features, aspects and advantages of the
disclosure will become
apparent from the following description, appending claims and the accompanying
drawing,
which is briefly described below.
[0019] Figure 1 is a schematic of a process configuration of a
disclosed process.
[0020] Figure 2 is a schematic of a process configuration of a disclosed
process.
[0021] It should be noted that these figures are merely examples and
no limitations on
the scope of the present disclosure is intended thereby. Further, the figures
are generally not
drawn to scale, but are drafted for purposes of convenience and clarity in
illustrating various
aspects of the disclosure.
DETAILED DESCRIPTION
[0022] For the purpose of promoting an understanding of the
principles of the
disclosure, reference will now be made to the features illustrated in the
drawings and specific
language will be used to describe the same. It will nevertheless be understood
that no
limitation of the scope of the disclosure is thereby intended. Any alterations
and further
modifications, and any further applications of the principles of the
disclosure as described
herein are contemplated as would normally occur to one skilled in the art to
which the
disclosure relates. It will be apparent to those skilled in the relevant art
that some features that
are not relevant to the present disclosure may not be shown in the drawings
for the sake of
clarity.
[0023] At the outset, for ease of reference, certain terms used in
this application and
their meaning as used in this context are set forth below. To the extent a
term used herein is
not defined below, it should be given the broadest definition persons in the
pertinent art have
given that term as reflected in at least one printed publication or issued
patent. Further, the
present processes are not limited by the usage of the terms shown below, as
all equivalents,
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synonyms, new developments and terms or processes that serve the same or a
similar purpose
are considered to be within the scope of the present disclosure.
[0024] Throughout this disclosure, where a range is used, any number
between or
inclusive of the range is implied.
[0025] A "hydrocarbon" is an organic compound that primarily includes the
elements
of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or any
number of other
elements may be present in small amounts. Hydrocarbons generally refer to
components found
in heavy oil or in oil sand. However, the techniques described are not limited
to heavy oils but
may also be used with any number of other reservoirs to improve gravity
drainage of liquids.
Hydrocarbon compounds may be aliphatic or aromatic, and may be straight
chained,
branched, or partially or fully cyclic.
[0026] "Bitumen" is a naturally occurring heavy oil material.
Generally, it is the
hydrocarbon component found in oil sand. Bitumen can vary in composition
depending upon
the degree of loss of more volatile components. It can vary from a very
viscous, tar-like,
.. semi-solid material to solid forms. The hydrocarbon types found in bitumen
can include
aliphatics, aromatics, resins, and asphaltenes. A typical bitumen might be
composed of:
19 weight (wt.) % aliphatics (which can range from 5 wt. % - 30 wt. %, or
higher);
19 wt. % asphaltenes (which can range from 5 wt. % - 30 wt. %, or higher);
30 wt. % aromatics (which can range from 15 wt. % - 50 wt. %, or higher);
32 wt. % resins (which can range from 15 wt. % - 50 wt. %, or higher); and
some amount of sulfur (which can range in excess of 7 wt. %), the weight %
based
upon total weight of the bitumen.
In addition, bitumen can contain some water and nitrogen compounds ranging
from less than
0.4 wt. % to in excess of 0.7 wt. %. The percentage of the hydrocarbon found
in bitumen can
vary.
[0027] "Heavy oil" includes oils which are classified by the American
Petroleum
Institute ("API"), as heavy oils, extra heavy oils, or bitumens. The term
"heavy oil" includes
bitumen as well as lighter materials that may be found in a sand or carbonate
reservoir. Heavy
oil may have a viscosity of about 1,000 centipoise (cP) or more, 10,000 cP or
more, 100,000
cP or more, or 1,000,000 cP or more. In general, a heavy oil has an API
gravity between 22.3
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API (density of 920 kilograms per meter cubed (kg/m3) or 0.920 grams per
centimeter cubed
(g/cm3)) and 10.00 API (density of 1,000 kg/m3 or 1 g/cm3). An extra heavy
oil, in general,
has an API gravity of less than 10.00 API (density greater than 1,000 kg/m3 or
1 g/cm3). For
example, a source of heavy oil includes oil sand or bituminous sand, which is
a combination
of clay, sand, water and bitumen.
[0028] "Fine particles" or "fines" are generally defined as those
solids having a size
of less than 44 microns (gm), as determined by laser diffraction particle size
measurement.
[0029] "Coarse particles" are generally defined as those solids
having a size of greater
than 44 microns (gm).
[0030] The term "solvent" as used in the present disclosure should be
understood to
mean either a single solvent, or a combination of solvents.
[0031] The terms "approximately," "about," "substantially," and
similar terms are
intended to have a broad meaning in harmony with the common and accepted usage
by those
of ordinary skill in the art to which the subject matter of this disclosure
pertains. It should be
understood by those of skill in the art who review this disclosure that these
terms are intended
to allow a description of certain features described and claimed without
restricting the scope
of these features to the precise numeral ranges provided. Accordingly, these
terms should be
interpreted as indicating that insubstantial or inconsequential modifications
or alterations of
the subject matter described and are considered to be within the scope of the
disclosure.
[0032] The articles "the", "a" and "an" are not necessarily limited to mean
only one,
but rather are inclusive and open ended so as to include, optionally, multiple
such elements.
[0033] The term "paraffinic solvent" (also known as aliphatic) as
used herein means
solvents comprising normal paraffins, isoparaffins or blends thereof in
amounts greater than
50 wt. %. Presence of other components such as olefins, aromatics or
naphthenes may
counteract the function of the paraffinic solvent and hence may be present in
an amount of
only 1 to 20 wt. % combined, for instance no more than 3 wt. %. The paraffinic
solvent may
be a C4 to C20 or C4 to C6 paraffinic hydrocarbon solvent or a combination of
iso and normal
components thereof. The paraffinic solvent may comprise pentane, iso-pentane,
or a
combination thereof.
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[0034] The production of higher value products materials from the
lower (or lowest)
value components of bitumen is valuable to improve the economics of bitumen
upgrading.
Disclosed herein is a process involving the processing of heavy hydrocarbon
feedstocks, such
as bitumen froth, bitumen, heavy crude oil and/or atmospheric and vacuum
residues derived
from these feedstocks to produce a non-combustion carbon product, such as high-
performance
and general purpose carbon fibers, carbon-carbon composites, and carbon foams.
The process
may use oil sand production and refinery processing units, including
paraffinic froth treatment
(PFT), visbreaking/coking, distillation, solvent deasphalting and/or
hydroprocessing.
[0035] With reference to Figure 1, a disclosed method comprises
providing a heavy
hydrocarbon feedstock (102) comprising paraffinic froth treated bitumen and/or
solvent
de-asphalted bitumen; thermally cracking (104) the heavy hydrocarbon feedstock
(102) to
produce a cracked stream (106) and a gas (108); distilling (110) the cracked
stream (106) to
produce a distillation bottoms stream (112) and a naphtha and distillates
stream (114); and
de-asphalting (116) the distillation bottoms stream (112) to produce a pitch
fraction (118) and
de-asphalted oil (DAO) (120). A solvent (117) may be used for the de-
asphalting (116) step.
[0036] The heavy hydrocarbon feedstock may comprise less than 14 wt.
%
C5-asphaltenes.
[0037] The process may further comprise upgrading a bitumen stream
thereby
reducing its viscosity and density to produce the heavy hydrocarbon feedstock.
The upgrading
may comprise paraffinic froth treatment (PFT) or solvent de-asphalting. The
upgrading may
comprise precipitating out 25-75% by weight of native C5-asphaltenes using a
hydrocarbon
solvent comprising pentanes.
[0038] The thermal cracking may be effected at a temperature of 400C
to 520C for
a period of 10 to 120 minutes. The thermal cracking may be effected using a
visbreaker or a
coker.
[0039] The distillation may be effected at a cut point of 270C to
565C.
[0040] The step of de-asphalting the distillation bottoms stream may
comprise using
a hydrocarbon solvent with a carbon number ranging from C5 to C8.
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[0041] The step of de-asphalting the distillation bottoms stream may
comprise using
a solvent comprising pentanes, hexanes, heptanes, reformate, furfural, N-
methylpyrrolidone,
heavy coker gas oil, coker gas oil, light coker gas oil, light cycle oil,
toluene, naphthalene,
steam cracked gas oil, or a combination thereof. The step of de-asphalting the
distillation
bottoms stream may comprise a single de-asphalting step using a solvent with a
carbon
number of C5 to C8. The step of de-asphalting the distillation bottoms stream
may comprise
two de-asphalting steps in series to produce a pitch fraction with a reduced
level of
contaminants and/or impurities and/or higher molecular weight compounds. The
two
de-asphalting steps may comprise a first de-asphalting step using first
solvent and a second
de-asphalting step using a second solvent, wherein the second solvent has a
lower solubility
parameter than that of the first solvent.
[0042] The process may further comprise pyrolyzing the pitch fraction
to produce a
mesophase pitch or a modified isotropic pitch. The pyrolyzing may be effected
at a
temperature of 375C to 500T for a period of 10 to 180 minutes.
[0043] The process may further comprise converting the pitch fraction into
a
non-combustion carbon product. The non-combustion carbon product may be a
carbon fiber,
carbon-carbon composite, or carbon foam. The process may further comprise
spinning,
extruding, stabilizing, carbonizing, or surface treating the non-combustion
carbon product.
The process may further comprise melt blowing the mesophase pitch to produce a
fiber mat
or chopped fibers.
[0044] The process may further comprise sparging of a gas through the
pitch fraction
to volatilize light fractions.
[0045] The process may further comprise combining the naphtha and
distillates stream
with the DA0 to produce a partially upgraded bitumen (PUB) stream. The PUB may
have a
viscosity less than 350 cSt at pipeline temperature.
[0046] The process may further comprise hydro-refining the naphtha
and distillates
stream for reducing an olefin content to produce a hydro-refined stream.
[0047] The process may further comprise a hydro-processing or
oxidation step, before
or after the thermal cracking step for reducing the sulfur content.
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[0048] The process may further comprise filtering the cracked stream
for reducing a
particulate matter content.
[0049] A carbon fiber composite may comprise the carbon fiber
described herein, and
having a matrix material comprising a thermoset matrix, a thermoplastic
matrix, cement,
concrete, ceramic, a metal, a metal alloy, or a combination thereof. Examples
of thermoset
polymers are cyclopentadiene, dicyclopentadiene, epoxy, pitch, phenolic
resins, vinylester,
polyimide and polyesters. Examples of thermoplastic polymers are polyethylene,
polypropylene, high-density polyethylene, linear low-density polyethylene, low-
density
polyethylene, polyamides, polyvinylchloride, polyetheretherketone,
polyetherketoneketone,
polyaryletherketone, polyetherimide and polyphenylene sulfide.
[0050] The heavy hydrocarbon feedstock may be in the form of bitumen
froth
produced via oil sands mining or diluted bitumen obtained via in-situ
production, or the
residue fraction derived from bitumen. The heavy hydrocarbon feedstock may be
processed
to produce a lower viscosity/density and higher quality upgraded bitumen
stream that requires
significantly less diluent to be blended (0-10 volume %) to meet pipeline
specifications (for
instance, per Table 1). The produced pitch stream may be used to manufacture
higher value
non-combustion materials (e.g. carbon fibers or carbon-carbon composites). The
disposition
of the lower (or lowest) value components of bitumen into these higher value
products,
compared to conventional petroleum coke or a solids waste stream, may improve
the
economics associated with upgrading bitumen/heavy oil. Moreover, it may reduce
the carbon
footprint and green-house gases associated with bitumen production/processing.
[0051] The heavy hydrocarbon feedstock, such as bitumen froth,
bitumen, heavy
crude oil and/or atmospheric and vacuum residues derived from these feedstocks
may be
processed to produce a variety of different non-combustion carbon products,
including
high-performance and general purpose carbon fibers, carbon-carbon composites,
and carbon
foams.
[0052] Light gas byproducts from thermal cracking (e.g. methane,
ethane, ethylene,
propane, propylene, butanes, butylenes) may be used as a plant fuel source.
[0053] With reference to Figure 2, a disclosed method adds hydro-
refining and
pyrolysis/conversion steps to Figure 1. With reference to Figure 2, a
disclosed method
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comprises providing a heavy hydrocarbon feedstock (202) comprising paraffinic
froth treated
bitumen and/or solvent de-asphalted bitumen; thermally cracking (204) the
heavy
hydrocarbon feedstock (202) to produce a cracked stream (206) and a gas (208);
distilling
(210) the cracked stream (206) to produce a distillation bottoms stream (212)
and a naphtha
and distillates stream (214); and de-asphalting (216) the distillation bottoms
stream (212) to
produce a pitch fraction (218) and de-asphalted oil (DAO) (220). A solvent
(217) may be
used for the de-asphalting (216) step. The naphtha and distillates stream
(214) may be
hydro-refined (222) for reducing an olefin content to produce a hydro-refined
stream (224).
The hydro-refined stream (224) may be combined with the DA0 (220) to produce
partially
upgraded bitumen stream (226). The pitch fraction (218) may be pyrolyzed and
converted
(228) to a non-combustion product (230) as described herein.
[0054] The produced pitch fraction will have a certain wt.%, MCRT
(Micro Carbon
Residue Test), softening point, and mesophase content (for an isotropic pitch,
mesophase
content should = 0, or be very low at least). Upon additional pyrolysis, a
modified isotropic
pitch can form, which will have an MCRT, and TSP (Softening Point Temperature)
greater
than the original pitch fraction, but still 0 mesophase content. If pyrolysis
goes further, a
mesophase pitch can form which now has a mesophase content greater than 0 and
a softening
point and MCRT greater than the pitch fraction or the modified isotropic
pitch. Quinoline
insoluble (QI) can also be another property used to benchmark the pitch. Once
the desired
pitch has been formed, it can be converted to form a carbon article. This
manufacture step
may involve a pyrolysis step, optionally with stabilization step to convert
the hydrocarbon
molecules into a solid block of carbon, which does not flow.
[0055] Experimental
[0056] Experimental pilot and bench-scale units were used to generate
pitch using
bitumen as the feed. The data below demonstrate the ability of a process
described herein to
produce both isotropic and mesophase pitch materials suitable for a variety of
applications, in
particular carbon fiber production, while producing partially upgraded bitumen
(PUB).
[0057] Pitch generated from PFT treated bitumen via:
[0058] Visbreaking the PFT treated bitumen at 430-435C, 33 min
(average equivalent
reaction time (ERT) = 2600s at 800T) followed by distillation to generate: a
naphtha
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distillate cut (<270'C), which was subsequently hydroprocessed; a gas oil cut;
and a heavy
resid cut (>480'C).
[0059] Deasphalting the heavy resid cut using C7 solvent at 220 C,
700psi, 6:1
solvent/oil (S/O) ratio, resulting in a pitch fraction and a DAO. The DA0 was
then blended
with the hydroprocessed naphtha cut to generate a PUB.
[0060] The pitch fraction generated from the PFT treated bitumen
using the
visbreaking and deasphalting conditions specified above was analyzed for
softening point and
mesophase content (%) pre- and post-heat treatment (pyrolysis). The presence
of mesophase
was apparent following the application of heat treatment to the pitch.
[0061] The corresponding PUB generated from the PFT treated bitumen using
the
visbreaking and deasphalting conditions specified above showed a significant
improvement
in quality relative to the feed, as shown in Table 2. The PUB viscosity and
density met the
pipeline specifications without the need for diluent blending.
Table 2. PUB properties after upgrading
PFT
PUB
Bitumen
Yield (wt%) 86
Viscosity (cSt) at 10 C 125,000 <350
API Gravity ( ) 8.6 19.0
Diluent req' d (v%) 30 0
Sulfur (wt%) 4.4 2.9
MCR (wt%) 11.4 4.0
TAN (mgKOH/g) 2.8 0.3
[0062] It should be understood that numerous changes, modifications,
and alternatives
to the preceding disclosure can be made without departing from the scope of
the disclosure.
The preceding description, therefore, is not meant to limit the scope of the
disclosure. Rather,
the scope of the disclosure is to be determined only by the appended claims
and their
equivalents. It is also contemplated that structures and features in the
present examples can be
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altered, rearranged, substituted, deleted, duplicated, combined, or added to
each other. The
scope of the claims should not be limited by particular embodiments set forth
herein, but
should be construed in a manner consistent with the specification as a whole.
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