U.S. patent application number 16/227515 was filed with the patent office on 2019-06-27 for method for producing pipeline specification bitumen from oil sands mining and extraction facilities using non-miscible solvents .
The applicant listed for this patent is USO (UTAH) LLC. Invention is credited to Joseph Fournier, Tyler Layne LaValley.
Application Number | 20190194548 16/227515 |
Document ID | / |
Family ID | 66948246 |
Filed Date | 2019-06-27 |
United States Patent
Application |
20190194548 |
Kind Code |
A1 |
Fournier; Joseph ; et
al. |
June 27, 2019 |
METHOD FOR PRODUCING PIPELINE SPECIFICATION BITUMEN FROM OIL SANDS
MINING AND EXTRACTION FACILITIES USING NON-MISCIBLE SOLVENTS AND
CENTRIFUGE PROCESSING
Abstract
A method of producing pipeline quality bitumen, includes the
steps of: receiving bitumen diluted with a diluent solvent from a
secondary froth treatment process; thermally dehydrating the
diluted bitumen at a temperature above about 100.degree. C. and
below the boiling point of the diluent solvent; mixing a
high-density, non-miscible solvent (HD-NMS) and optionally, a low
density, miscible solvent (LD-MS) to the diluted bitumen; and
separating any remaining fine solids and precipitates by
gravitational separation at a temperature above about 100.degree.
C. and below the boiling point of the diluent solvent.
Inventors: |
Fournier; Joseph; (Calgary,
CA) ; LaValley; Tyler Layne; (Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
USO (UTAH) LLC |
New York |
NY |
US |
|
|
Family ID: |
66948246 |
Appl. No.: |
16/227515 |
Filed: |
December 20, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62609165 |
Dec 21, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 1/045 20130101;
C10G 1/065 20130101 |
International
Class: |
C10G 1/06 20060101
C10G001/06; C10G 1/04 20060101 C10G001/04 |
Claims
1. A method of producing pipeline quality bitumen, comprising the
steps of: (a) receiving bitumen diluted with a diluent solvent from
a secondary froth treatment process; (b) thermally dehydrating the
diluted bitumen at a temperature above about 100.degree. C. and
below the boiling point of the diluent solvent; (c) mixing a
high-density, non-miscible solvent (HD-NMS) and optionally, a low
density, miscible solvent (LD-MS) to the diluted bitumen; and (d)
separating any remaining fine solids and precipitates by
gravitational separation at a temperature above about 100.degree.
C. and below the boiling point of the diluent solvent.
2. The method of claim 1 further comprising the step of recovering
and reusing the HD-NMS and optionally the LD-MS.
3. The method of claim 1 wherein the HD-NMS has a specific gravity
at least about 0.1 larger than the diluted bitumen and a dielectric
constant greater than about 20.
4. The method of claim 3 wherein the HD-NMS comprises
acetylacetone, dimethyl-formamide, or propylene glycol, or mixtures
thereof.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the treatment of solvent-diluted
bitumen produced in an oil sands bitumen extraction facility prior
to solvent recovery, and particularly a method which produces
pipeline specification bitumen without resorting to upgrading or
carbon rejection at any time.
BACKGROUND
[0002] Oil sands ore, known as bituminous sands, comprises a
naturally occurring mixture of water, bitumen and a mineral phase
comprising sand and clay. Oil sands ore may vary in quality and
character from region to region, or deposit to deposit. Generally,
Athabasca oil sands in Canada comprises water-wet sand grains,
while Utah oil sands in the United States comprises oil-wet sand
grains.
[0003] Oil sand mining and extraction processes are used to
liberate and separate bitumen from the water and mineral phases
such that the bitumen can be further processed to produce market
specification grade crude oil. Numerous oil sands mining and
bitumen extraction processes have been developed and
commercialized, all of which involve the use of water as the
processing medium. The role of water is to provide sensible heat to
enhance bitumen liberation through viscosity reduction, to produce
a fluid that can be pumped and to create an environment in which
gravimetric separation can develop. One such water extraction
process is the Clark Hot Water Extraction Process, which was the
first commercially successful oil sand extraction process.
[0004] A water-based extraction processes, such as the Clark
Process, typically requires that mined oil sand first be
conditioned for extraction by being crushed to a desired lump size
and then combined with hot water and caustic to form a conditioned
slurry of bitumen, water, sand, fine particles and entrained air
bubbles. In water-based extraction processes, the water is commonly
heated to about 65.degree. to 80.degree. C., and an amount of
sodium hydroxide is added to the slurry to adjust or maintain the
slurry pH upwards, which enhances the separation of bitumen from
the oil sand. The addition of sodium hydroxide (caustic) is
intended to elevate the concentration of natural surfactants
through an acid-base reaction with organic acids present in the
bitumen, and to increase the softness of the water phase by
increasing the concentration of sodium ions. Other water-based
extraction processes may have other temperature requirements and
may include other conditioning agents which are added to the oil
sand slurry.
[0005] Air entrainment and dispersion in ore processing and
hydrotransport is considered an essential component of effective
primary bitumen separation and recovery in conventional water based
extraction processes. The mechanism of air bubble attachment onto
bitumen surfaces aid in gravimetric separation of oil within
primary separation columns. Extensive aeration of the oil sands
slurry requires subsequent de-aeration in dedicated vessels after
the coarse mineral is rejected in the first stage of primary
extraction. As steam is often used in dearation, this additional
process step adds to the energy intensity required, which
translates to higher capital and operating costs. Likewise, the
reliance on hydrotransport retention time to achieve optimal
conditioning further adds to capital and operating costs due to
extensive pipeline wear. Also, it is commonly believed that the
substantial mechanical energy added during standard ore processing
and hydrotransport may be partly responsible for the limited
ability to achieve rapid fines consolidation within mineral
retention times in primary and secondary extraction stages.
[0006] Water-based primary bitumen extraction processes typically
result in the production of a number of product streams, some of
which are disposed of as waste. For example, these streams include
a bitumen froth stream comprising of aerated bitumen, residual fine
particulate mineral solids and water, a middlings stream comprising
bitumen with entrained fine particulate mineral solids and water,
and a coarse tailings stream consisting primarily of coarse
particulate mineral solids and water. The coarse tailings stream is
not typically processed further, since the coarse particulate
solids are relatively easy to dispose of and do not typically
present a significant environmental risk. The bitumen froth stream
and the middlings stream are typically processed further, both to
recover or purify bitumen and to render the fine solids more
readily disposable and less of an environmental hazard. Froth
treatment typically involves introduction of either heavy
naphthenic (naphthenic froth treatment or NFT) or light paraffinic
(paraffinic froth treatment or PFT) solvents to produce a high oil
content bitumen stream which is low in fines and water content.
Subsequent stages of extraction are those associated with solvent
recovery from separate fine mineral solids slurry and solvent
diluted bitumen streams. The fine mineral solids and water
recovered from the bitumen froth stream are typically ultimately
disposed of in tailings ponds, where subsequent consolidation of
the fine solids occurs and the water recovered and reused.
[0007] Pipeline specification oil must have a basic sediment and
water (BS&W) content of less than 0.5 vol %. NFT bitumen fed
upgraders and PFT extraction facilities achieve final product
quality, in terms of residual BS&W, by means of deep carbon
rejection. Additionally, diluted bitumen (DB) from NFT extraction
expose overhead systems in upgraders to acid gas corrosion caused
by hydrochloric acids generated by dissolved chlorides that
hydrolyze residual process water and by reacting with native
organic acids in the DB feed. The risk of fires in upgraders,
caused by overhead corrosion, is increasing as water usage has been
decreasing and with improvements in fine tails dewatering that
collectively cause chloride salts in process water, released from
ore connate water, to increase in concentration at an accelerated
rate.
[0008] Traditional models of the tight water-in-oil (W/O) emulsions
that exist in naphtha diluted bitumen entering upgrading facilities
from both overflow of inclined plate separators (IPS) and disk
stack centrifuges (DSC), commonly illustrate the presence of
adsorbed semi-solid organics (asphaltenes) and ultrafine minerals
at the water/oil (W/O) interface, which act to inhibit coalescence
and separation by increasing the interfacial tension of the W/O
interface. The limit to which NFT extraction can separate process
water and sediment is not sufficient to produce diluted bitumen
with BS&W below 0.5 vol. %. Furthermore, it is widely believed
that these residual solids and interfacially adsorbed asphaltenes
in NFT DB cause upset conditions in downstream desalter units when
attempts have been made to by-pass the midstream and directly feed
into a refinery.
[0009] PFT extraction facilities achieve a final product quality
that exceeds minimum pipeline quality requirements by using
paraffin injection in froth treatment, which causes
co-precipitation of ultrafine minerals and residual W/O emulsions,
together with asphaltenes that are insoluble in bitumen when
exposed to higher ratios of C5/6 paraffin solvent loading. In this
sense, both NFT+upgrading and PFT extraction reject large
quantities (8 to 20 wt. %) of bitumen in achieving minimum pipeline
specification for BS&W.
[0010] It is known to add (e.g., CA Patent No. 2,647,964) low
carbon number alcohols such as methanol, ethanol, or isopropanol to
naphthenic froth or NFT DB upgrader feed, to destabilize the
surface tension of the W/O interface and enhance the ability of W/O
emulsions to coalesce, thereby giving rise to lower BS&W in the
final product. Due to the immiscibility of alcohols in DB and its
higher miscibility in process water, alcohols act to destabilize
the W/O interfacial tension by reducing the dielectric constant of
the residual water in froth or NFT DB. However, this methodology
results in the formation of azeotropic mixtures of the process
water and the alcohol.
[0011] This prior art use of solvents with dielectric constants
lower than water ({acute over (.epsilon.)}=80) to improve crude
quality was motivated by the physical chemistry fundamentals used
in the ASTM methods D664 and D974 to quantify native organic acids
in heavy crudes (i.e., Total Acid Number or TAN). In these ASTM
methods, caustic isopropyl alcohol, with an intermediate dielectric
constant ({acute over (.epsilon.)}=20), is used to selectively
extract and neutralize native organic acids in heavy crudes ({acute
over (.epsilon.)}=2.2), while remaining immiscible with the bulk of
the heavy crude sample. The general principle at work is that
compounds that form miscible solutions, commonly have similar
dielectric properties and thus miscibility is predictable.
SUMMARY OF THE INVENTION
[0012] The present invention comprises a two-stage process of
producing pipeline quality solvent-diluted bitumen. The objective
of the first stage is to dehydrate and collapse residual tight
water/oil emulsions present within the diluted bitumen (DB) which
may be produced using conventional separation processes such as
inclined plate separators (IPS's), cyclones and decanter or DSC
units. The objective of the second stage is to remove residual
BS&W using a non-miscible solvent and optionally a miscible
solvent to lower the specific gravity (SG) of the diluted
bitumen.
[0013] In one aspect, the invention comprises a bitumen extraction
system and method, which comprises steps to achieve a bitumen
stream with BS&W less than 0.5 vol. % from a diluted bitumen
stream resulting from secondary froth treatment. The bitumen has
been diluted with a diluent solvent, such as a biosolvent or
naphtha. After secondary froth treatment, an oil dehydrator vessel
is used to recover residual water by collapsing any residual
water-in-oil emulsions. The dehydrator operates above the boiling
point of water, but below the boiling point of the solvent. The DB
is then mixed with a high-density, non-miscible solvent (HD-NMS)
and optionally, a low density, miscible solvent (LDMS). Subsequent
steps takes the dehydrated diluted bitumen stream and, at or near
the same temperature, passes it through a gravimetric separator,
such as a centrifuge, to extract fine mineral and precipitated
salts. The diluted bitumen thus treated may then pass to a solvent
recovery stage.
[0014] Therefore, in one aspect, the invention may comprise a
method of producing pipeline quality bitumen, comprising the steps
of: [0015] (a) receiving bitumen diluted with a diluent solvent
from a secondary froth treatment process; [0016] (b) thermally
dehydrating the diluted bitumen at a temperature above about
100.degree. C. and below the boiling point of the diluent solvent;
[0017] (c) mixing a high-density, non-miscible solvent (HD-NMS) and
optionally, a low density, miscible solvent (LD-MS) to the diluted
bitumen; and [0018] (d) separating any remaining fine solids and
precipitates by gravitational separation at a temperature above
about 100 C and below the boiling point of the diluent solvent. The
solvents may subsequently be recovered, by distillation for
example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The following drawings form part of the specification and
are included to further demonstrate certain embodiments or various
aspects of the invention. In some instances, embodiments of the
invention can be best understood by referring to the accompanying
drawings in combination with the detailed description presented
herein. The description and accompanying drawings may highlight a
certain specific example, or a certain aspect of the invention.
However, one skilled in the art will understand that portions of
the example or aspect may be used in combination with other
examples or aspects of the invention.
[0020] FIG. 1 shows a process flow diagram of one embodiment of a
method of the present invention.
[0021] FIG. 2 shows a process flow diagram of an alternative
embodiment of a method of the present invention.
[0022] FIG. 3 shows a cross-sectional schematic of a disc stack
centrifuge.
[0023] FIG. 4 shows a cross-sectional schematic of an alternative
embodiment of a disc stack centrifuge.
DETAILED DESCRIPTION
[0024] As used herein, certain terms have the meanings defined
below. All other terms and phrases used in this specification have
their ordinary meanings as one of skilled in the art would
understand.
[0025] The present invention relates to an improvement to a process
of extracting bitumen from oil sands ore.
[0026] Oil sands ore is typically mined and crushed to break down
large chunks. The creation of a water-based oil sands ore slurry is
known as wet ore processing. Elements of oil sands extraction
methods are described in co-owned U.S. Pat. No. 8,758,601,
co-pending U.S. patent application Ser. No. 14/959,910--Oilsands
Processing Using Inline Agitation and an Inclined Plate Separator,
filed Dec. 4, 2015, or U.S. patent application Ser. No. 15/453,318
entitled Process Water Chemistry in Bitumen Extraction from Oil
Sands filed March 8, 2017, or U.S. patent application Ser. No.
15/467,583, entitled Solvent Addition in Water Based Oil Sands Ore
Digestion and Primary Extraction, filed Mar. 23, 2017, or U.S.
patent application Ser. No. 15/494,367, entitled Method for
Producing Pipeline Specification Bitumen from Oil Sands Mining and
Extraction Facilities, filed Apr. 21, 2017, the entire contents of
each which are incorporated herein by reference for all purposes,
where permitted.
[0027] In one embodiment, the methods described herein contemplate
the use of any suitable solvent or solvent mixture as the primary
diluent solvent. For example, the solvent may comprise a
"biosolvent" which is a liquid substance which is substantially
soluble in bitumen, and which has a biological origin. Exemplary
biosolvents may include terpenes such as, without limitation,
pinene or limonene. Terpenes may be acidic, which may necessitate
the use of a basic sodium salt to neutralize organic acids and to
limit solubility of components of the mineral phase which may
hinder bitumen extraction. Ultimately, the invention may apply to
any solvent formulation applied in the early stages of primary
extraction and in particular in ore digestion and
hydrotransport.
[0028] In other embodiments, the diluent solvent may comprise
naphtha or a paraffinic solvent as may be used in a conventional
NFT or PFT process.
[0029] At least in the case of biosolvents, it may be preferable to
add the solvent to the slurry during the early stages of ore
conditioning, whether in rotating drums or by hydrotransport, which
may increase bitumen recovery in the subsequent water-based
separation steps, allowing for lower temperature separation
efficiency, for example at temperatures less than about 60.degree.
C. or less than about 45.degree. C., and the co-production of a
stackable fine mineral solid stream. Without restriction to a
theory, application of solvent in the ore conditioning step is
believed to be part of the reason why fine minerals dispersed into
the slurry are able to be dewatered or consolidated above their
liquid limit (Atterberg Limit) in subsequent separation stages
further downstream using conventional centrifugal processing. The
action of solvents during ore conditioning is believed to be at
least one causal factor in reducing interfacial repulsion between
fine mineral particles, such that relatively low mechanical
centrifuge treatment in extraction is able to produce a soil-like
dewatered mineral stream.
[0030] In one embodiment, diluent solvent is added at a rate
relative to the known bitumen saturation and ore feed rate into ore
conditioning and is reported as a ratio of weight of solvent to
weight of bitumen. This ratio may vary from about 0.25:1 to about
2:1. The ratio depends at least in part on the grade and type of
ore. Higher grades of oil sands ore may comprise up to about 12 wt
% bitumen while lower grade may be around 7 wt % bitumen. Lower ore
grades may benefit from a greater solvent proportion and oil-wet
ore types commonly require higher ratios than water-wet oil sands
ore to achieve comparable bitumen separation efficiencies. The
amount of solvent added is not intended to "extract" the bitumen
into a solvent phase. Rather, the amount of solvent is selected so
as to be entirely dissolved into the bitumen phase. In one
embodiment, there is substantially no free solvent in the slurry
after the conditioning phase.
[0031] In one embodiment, sufficient water and solvent is added
such that the density of the slurry ranges between about 25 to
about 60 wt % solids, preferably about 35 to 45% wt % solids.
[0032] The solvent-assisted ore conditioning step of the present
invention may be used in conjunction with any water-based bitumen
separation or extraction process, including commercially practiced
Karl Clark extraction methods.
[0033] In one embodiment, once the ore has been suitably
conditioned with the addition of the solvent, the slurry passes to
a primary separation stage, using the primary separation vessels
(PSV1 and PSV2) shown in FIG. 1. In the PSVs, counter current lift
water is added to produce a state of hindered settlement in each of
the two separation vessels arranged in series. The bottom stream
from the first separation vessel acts as feed to the second
separation vessel. The bottom stream from the second separation
vessel then is fed to a screen shaker unit for dewatering of the
coarse tails stream. Separation in the PSVs is the core of the
process, where the bitumen is stripped from the host sandstone,
which comprises quartz, feldspar, plagioclase and minor percentages
of clay minerals, using heat and water. The biosolvent has absorbed
into the bitumen phase during conditioning and facilitates this
separation. During the separation phase, the solvent-diluted
bitumen bond with the sand and clays is more easily broken. The
lower specific gravity of the diluted bitumen allows for more
effective gravity separation from the water phase to occur.
[0034] The diluted bitumen follows the overflow from the primary
separation vessels but is still mixed with a significant amount of
water and fine solids. A secondary separation stage which utilizes
a bulk separator produces a water phase, and a diluted bitumen
stream which includes fine solids. In one embodiment, the secondary
separation stage may comprise an agitator and an inclined plate
separator.
[0035] Inclined plate separators (IPS) function to reduce the water
volumes reporting to downstream centrifuge units. This may be
achieved by agitating the mixture from the PSVs in an inline mixer,
such that both diluted bitumen and fines exit via the underflow
stream of the IPS, while the overflow being predominately process
water. The overflow stream from a first IPS unit may then be
treated in a second IPS unit. The overflow from the second IPS unit
is relatively clean process water and may be used as recycle water.
The underflow from both IPS units may then be combined and treated
in a decanter (decanting centrifuge) which separates fine solids
and outputs diluted bitumen with entrained water and residual fine
solids.
[0036] In alternative embodiments, the diluted bitumen may be used
as produced by a NFT process.
[0037] In any case, the diluted bitumen from the secondary froth
treatment (or from a NFT process) will contain about 1.0 to about
2.0% BS&W at this stage. The first step in further processing
is to use a dehydration unit (or water recovery unit) to remove
substantially all remaining water, which likely remains only in
microemulsions within the diluted bitumen. The dehydrator operates
at an elevated temperature, preferably above the boiling point of
water, but below the boiling point of the diluent solvent. Where a
mix of solvents is used, it is preferred to limit the temperature
below the lowest boiling point of any substantial component of the
solvent mixture. Without restriction to a theory, it is believed
that such thermal treatment of wet diluted bitumen prior to solvent
recovery, water micelles are collapsed through evaporation, and
dissolved solids are precipitated, including chloride anions.
[0038] The intermediate temperature regime of the water recovery
unit acts to further reduce the viscosity of the crude oil,
eliminates sterically hindered tight W/O emulsions, which allows
for the use of organic acid extracting solvents that would
otherwise form azeotropic solutions with residual process water. If
the diluted bitumen came from an NFT extraction facility, the water
recovery unit will largely evaporate residual process water at
lower temperatures where chloride hydrolysis does not develop, for
example in the range of about 100.degree. C. to about 130.degree.
C.).
[0039] The boiling point of terpenes is typically in the range of
about 150.degree. C. to about 185.degree. C. Therefore, a preferred
range of thermal treatment may be in the range of about 100.degree.
C. to about 150.degree. C., more preferably about 120.degree. C. to
about 140.degree. C. In some cases, it may be preferable to
maintain the temperature below about 130.degree. C., above which
chloride hydrolysis is more likely to occur.
[0040] In one embodiment, the dehydrated diluted bitumen then moves
into a second stage of treatment that is comprised of a solvent
mixer, a disc stack centrifuge and two parallel solvent recovery
systems. The purpose of the second stage is to extract residual
ultrafine solids and precipitated salts from the evaporated process
water. Also, the total acid number (TAN) may be reduced or
eliminated within the bitumen final product.
[0041] In the mixer, the HD-NMS is added. The HD-NMS is selected
based on numerous important physical properties, particularly its
dielectric constant ({acute over (.epsilon.)}), density, boiling
point and cost per tonne. This solvent preferably has a SG that is
greater than, preferably at least 0.1 greater, than the diluted
bitumen (DB) and a {acute over (.epsilon.)} value ranging from, for
example, 20 to 40, in order to limit its miscibility in the DB
({acute over (.epsilon.)}=2). It will still function as an
effective solvent for organic acids within the DB. As with
isopropyl alcohol used in ASTM methods D664 and D974, the {acute
over (.epsilon.)} of this high density non-miscible solvent
(HD-NMS) will solubilize caustic salts (e.g., NaOH), which will in
turn facilitate caustic-organic acid (TAN) neutralization reactions
when organic acids are extracted from the DB. Likewise, the HD-NMS
will solubilize the organic ions that are the by-products of TAN
neutralization.
[0042] Suitable HD-NMS may include acetylacetone,
dimethyl-formamide, or propylene glycol, or mixtures thereof.
Desirable properties of these solvents are shown in Table 1
below:
TABLE-US-00001 STP STP STP Dielectric Specific Boiling
.DELTA.H.sub.Vap Candidate HD-NMS Constant ({acute over (.di-elect
cons.)}) Gravity Point (.degree. C.) (kJ/mole) Acetylacetone 25
0.975 140 40 Dimethyl-formamide 38 0.9445 153 48 Propylene Glycol
32 1.036 188 56
[0043] The HD-NMS may be added to the diluted bitumen in between
about 1 wt. % to about 50 wt. % and preferably between about 20 wt.
% to about 30 wt. %.
[0044] The optional LD-MS is fully miscible in the dehydrated dirty
crude and acts to reduce its density, viscosity and dielectric
constant. Examples of a low density miscible solvent (LD-MS)
include light naphtha and C6/7 paraffins ({acute over
(.epsilon.)}=1.8), which are added in sufficient quantities such
that the resulting DB achieves a specific gravity (SG) less than
the HD-NMS solvent, preferably at least about 0.05, more preferably
at least about 0.10, less than the HD-NMS solvent. Dissolving C6/7
paraffins in the bitumen fraction at a solvent-to-bitumen (SB)
ratio of approximately 1:1 (by weight) will also act to initiate
the early stage precipitation of high specific gravity asphaltenes.
As with PFT extraction, injection of C6/7 paraffins near a S:B
ratio of 1:1 will effectively sequester ultrafine minerals in the
asphaltene precipitates that form. However, due to the higher
temperatures of gravimetric separation in stage II (100.degree. to
130.degree. C.) and the high centrifugal forces of the disk stack,
sedimentation rates will be orders of a magnitude higher than the
normal gravity separation conditions used in PFT extraction.
Therefore, the use of C6/7 paraffins to create a light DB phase in
the disk stack may create a high throughput pathway to decrease
sediment content to at least as low as 100 ppm on a bitumen
basis.
[0045] After the HD-NMS and the optional LD-MS are mixed into
dehydrated DB, the non-miscible mixture is fed into a disc stack
centrifuge unit where the HD-NMS solvent will extract the higher
density impurities (e.g., ultrafine minerals, precipitated salts
and asphaltenes) from the lighter DB phase, and will collectively
accelerate towards the heavy phase discharge ports along the outer
periphery of the centrifuge (FIG. 3). The heavy and light phases
exiting the high G centrifuge will then be pumped to their
respective distillation units that will recycle the LD-MS and
HD-NMS solvents back to the front end of stage two.
[0046] It is preferable to maintain the DSC under pressure to avoid
vaporization of the LD-MS, as the boiling point of the LD-MS may be
below the process temperature used in the mixing and gravimetric
separation stages.
[0047] In a preferred embodiment, the disk stack centrifuge is
configured to allow a HD-NMS fluid to also be injected into the
peripheral side region of the disk stack, and that a process
control will be used to regulate a constant distance between the DB
enriched fluid concentrated along the inside vertical axis and the
HD-NMS enriched fluid concentrated along the outside of the disk
stack wall. This mode of operability that regulates the distance of
the interface between both fluid types at a set distance from the
effluent nozzles located along the disk stack wall would be
achieved through adjusting separately feed rates of both the DB and
HD-NMS phases, and in particular the feed rate of the supplemental
HD-NMS fluid through a separate import nozzle located near the side
wall of the disk stack. This type of disk stack is often called a
self regulating interface nozzle bowl. By using a self-regulating
interface (SRI) mode of operation, this configuration will limit
the occurrence of DB fluids from unintentional discharging through
the heavy phase nozzles or effluent ports and thus hindering its
economic performance.
[0048] FIG. 2 illustrates one embodiment, where the extraction
solvent recovery occurs at the same stage where residual process
water is recovered and a self-regulating interface (SRI) DSC is the
high G centrifuge. As drawn, the polished light phase DB flows to
an independent solvent recovery unit or SRU (50), which
fractionates LD-MS and HD-NMS solvents from the final product
bitumen. Likewise, the heavy phase impurity enriched HD-NMS stream
(25) is drawn to first pass through an inclined plate separator
(IPS) clarifier unit (60), which splits the impurities to the
underflow (UF) stream (26) and the clarified HD-NMS returns to the
solvent--bitumen Mixer through the overflow (OF) outlet (27). A
two-step HD-NMS recovery treatment is outlined that has the IPS UF
stream (26) reporting to a dedicated SRU (, followed by a final
rotary vacuum SRU to achieve maximum solvent recovery.
[0049] By using HD-NMS fluids with dielectric constants between 20
and 80 and densities higher than the diluted bitumen (DB) being
polished, said HD-NMS fluids can be effectively introduced into a
disk stack, either homogeneously mixed with the DB feed or into the
side wall volume element of a disk stack near the discharge nozzles
(ports), and under high separation forces will facilitate the
extraction of higher specific gravity residual solids and salts. By
using HD-NMS solvents with dielectric constants higher than the DB
(2 to 3), but lower than water (80), one will be able to introduce
trace amounts of caustic (e.g., NaOH, KOH) into the HD-NMS, which
will further facilitate the acid--base neutralization of organic
acids in the DB, as well as the subsequent extraction of both
reacted & unreacted organic acids from the DB phase and into
the HD-NMS phase. The HD-NMS fluid in this invention is functioning
as similarly seen in TAN extraction methods as outlined in the ASTM
D664 and D974 methods.
[0050] The second stage of the process is intended to recover
residual HD-NMS that exits the disk stack in the DB light phase
stream, as well as to purify the solids, salts, water, organic
acids and their reacted conjugate bases (sodium or potassium
naphthenate anions) that exited the disk stack with the HD-NMS
heavy phase. Both the light and heavy liquid phases exiting the
disk stack are processed in independent distillation processes,
which separate clean HD-NMS fluids from both streams and then
recycles the HD-NMS fluid back to the disk stack as a recirculating
process. The rate of the HD-NMS recycle is intended to follow the
rate of DB being fed into the disk stack, and it is maintained that
by using a NMS of higher density than the incoming DB feed in
conjunction with a disk stack, the overall volume of HD-NMS
required is minimized and its residence time in the process is
maximized.
[0051] In this two stage process, the dielectric constant of the
HD-NMS fluid should be high enough to maximize the amount of HD-NMS
fluid gravimetrically separated from the lighter DB phase and yet
not too high such that lower dielectric constant impurities such as
minerals, salts and organic acids in the DB are hindered in their
separation rates out of the DB and into the HD-NMS fluid. The
classical example of a disk stack functioning in this capacity is
in the gravimetric separation of cream from whole milk, wherein the
lower dielectric constant cream and the higher dielectric constant
water based milk form a non-miscible fluid that can be readily
separated into a heavy and light phase using a standard disk stack
centrifuge. Likewise, the dielectric constant of the LD-MS fluid
would be selected to be between 1.5 to 5, such that a close match
is made relative to the dielectric constant of diluted bitumen (2
to 3).
[0052] The resulting bitumen product is now substantially free of
water and solids, having a BS&W less than 0.5 wt. %. The
diluted bitumen may then be treated in a distillation unit to
recover the diluent solvent, leaving saleable bitumen product.
Approximately 98 to 99% of the solvent may be recovered with
distillation and is recycled to a holding tank for re-use. In
tailings dewatering and solvent recovery approximately 90 to 95% of
the circulating process water is recovered from the produced sand
and fines tailings to be recycled indefinitely until fractionally
lost to tailings discharge. Make up water and make up process
chemical aids may be added as necessary.
Definitions and Interpretation
[0053] The description of the present invention has been presented
for purposes of illustration and description, but it is not
intended to be exhaustive or limited to the invention in the form
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the invention. Embodiments were chosen and described
in order to best explain the principles of the invention and the
practical application, and to enable others of ordinary skill in
the art to understand the invention for various embodiments with
various modifications as are suited to the particular use
contemplated. To the extent that the following description is of a
specific embodiment or a particular use of the invention, it is
intended to be illustrative only, and not limiting of the claimed
invention.
[0054] The corresponding structures, materials, acts, and
equivalents of all means or steps plus function elements in the
claims appended to this specification are intended to include any
structure, material, or act for performing the function in
combination with other claimed elements as specifically
claimed.
[0055] References in the specification to "one embodiment", "an
embodiment", etc., indicate that the embodiment described may
include a particular aspect, feature, structure, or characteristic,
but not every embodiment necessarily includes that aspect, feature,
structure, or characteristic. Moreover, such phrases may, but do
not necessarily, refer to the same embodiment referred to in other
portions of the specification. Further, when a particular aspect,
feature, structure, or characteristic is described in connection
with an embodiment, it is within the knowledge of one skilled in
the art to combine, affect or connect such aspect, feature,
structure, or characteristic with other embodiments, whether or not
such connection or combination is explicitly described. In other
words, any element or feature may be combined with any other
element or feature in different embodiments, unless there is an
obvious or inherent incompatibility between the two, or it is
specifically excluded.
[0056] It is further noted that the claims may be drafted to
exclude any optional element. As such, this statement is intended
to serve as antecedent basis for the use of exclusive terminology,
such as "solely," "only," and the like, in connection with the
recitation of claim elements or use of a "negative" limitation. The
terms "preferably," "preferred," "prefer," "optionally," "may," and
similar terms are used to indicate that an item, condition or step
being referred to is an optional (not required) feature of the
invention.
[0057] The singular forms "a," "an," and "the" include the plural
reference unless the context clearly dictates otherwise. The term
"and/or" means any one of the items, any combination of the items,
or all of the items with which this term is associated.
[0058] As will be understood by one skilled in the art, for any and
all purposes, particularly in terms of providing a written
description, all ranges recited herein also encompass any and all
possible sub-ranges and combinations of sub-ranges thereof, as well
as the individual values making up the range, particularly integer
values. A recited range (e.g., weight percents or carbon groups)
includes each specific value, integer, decimal, or identity within
the range. Any listed range can be easily recognized as
sufficiently describing and enabling the same range being broken
down into at least equal halves, thirds, quarters, fifths, or
tenths. As a non-limiting example, each range discussed herein can
be readily broken down into a lower third, middle third and upper
third, etc.
[0059] As will also be understood by one skilled in the art, all
language such as "up to", "at least", "greater than", "less than",
"more than", "or more", and the like, include the number recited,
and such terms refer to ranges that can be subsequently broken down
into sub-ranges as discussed above. In the same manner, all ratios
recited herein also include all sub-ratios falling within the
broader ratio.
* * * * *