Note: Descriptions are shown in the official language in which they were submitted.
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NS-494/532
BITUMEN PRODUCTION FROM SINGLE OR MULTIPLE OIL SAND
MINES
FIELD OF THE INVENTION
The present invention relates generally to the extraction of bitumen
from oil sand and, more particularly, to a process and process line for
combining a number of oil sand slurry preparation, slurry conditioning and
separation processes into a unified operation.
BACKGROUND OF THE INVENTION
The oil sands in Northern Alberta constitute one of the largest
hydrocarbon reserves in the world. Oil sands are a combination of
bitumen, quartz sand, clay, water and trace minerals. Bitumen can be
recovered from oil sands using two main methods: open-pit mining and in
situ drilling. Approximately 20% of the oil sands lie close enough to the
earth's surface to be mined.
The key characteristic of Alberta oil sand that makes bitumen
economically recoverable is that the sand grains are hydrophilic and
encapsulated by a water film which is then covered by bitumen. The water
film prevents the bitumen from being in direct contact with the sand and,
thus, by slurrying mined oil sand with heated water, the bitumen is liberated
from the sand grains and moves to the aqueous phase. However, the
composition of oil sands varies from deposit to deposit and the recovery of
bitumen from a particular deposit will depend on a number of factors
including the grade of the oil sand, i.e., the bitumen content, the fines
content, the connate water chemistry, the minimum mining thickness, and
the ratio of total volume to bitumen in place. Hence, various processing
conditions have been developed for successful extraction of bitumen from
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=
oil sands, which processing conditions will be discussed in more detail
below.
It is well understood in the industry that the quality of the oil sand
has very significant effects on bitumen recovery. For example, a "low
grade" oil sand typically contains between about 6 to 10 wt.% bitumen with
greater than about 25 wt.% fines. An "average grade" oil sand typically
contains at least 10 wt.% bitumen to about 12.5 wt.% bitumen with about
to 25 wt.% fines and a "high grade" oil sand typically contains greater
than 12.5 wt.% bitumen with less than 15 wt.% fines. Fines are generally
10 defined as
those solids having a size less about 44 pm. The higher fines
concentration in low to average grade oil sand contributes to the difficulty
in
extracting the bitumen.
Further, final mine pit limits are also influenced by physical limits
such as lease limits, roadways, river courses, plant facilities, and
15 associated
necessary geotechnical offsets. The requirements for power
lines, pipeline corridors, communication lines, ditches, heavy equipment
haul roads, light vehicle access roads, etc. are all incorporated into mining
limits. Thus, generally, each mine pit (site) will have its own individual
unique limitations to overcome.
In view of all of the above, several different bitumen extraction
processes have been developed to deal with variations in oil sand ore at
various mine sites as well as other limitations as listed above. An oil sands
bitumen extraction process generally includes the following steps:
preparing an oil sand and water slurry from mined oil sand (slurry
preparation), conditioning the oil sand slurry (slurry conditioning), and
subjecting the oil sand slurry to a separation process to recover the
bitumen (bitumen separation) (collectively referred to generally as "bitumen
extraction process").
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As used herein "slurry preparation" means the preparation of a water
and oil sand slurry in a slurry preparation unit. As used
herein, "slurry
conditioning" means the digestion of oil sand lumps present in the oil sand
slurry, liberation of bitumen from sand-fines-bitumen matrix, coalescence of
liberated bitumen flecks into larger bitumen droplets and aeration of
bitumen droplets. As used herein, "bitumen separation" means the
separation of bitumen from the solids and water present in the conditioned
oil sand slurry, commonly in a separation vessel such as a gravity
separator.
One bitumen extraction process commonly used in the industry is
referred to herein as the "hot water process". In general terms, the hot
water process involves feeding the mined oil sand into a rotating tumbler
where it is mixed for a prescribed retention time (generally in the range of 2
to 4 minutes) with hot water (approximately 80-90 C), steam, caustic (e.g.,
sodium hydroxide) and naturally entrained air to yield a slurry that has a
temperature typically around 80 C. The bitumen matrix is heated and
becomes less viscous. Chunks of oil sand are ablated or disintegrated.
The released sand grains and separated bitumen flecks are dispersed in
the water. To some extent bitumen flecks coalesce and grow in size, They
may contact air bubbles and coat them to become aerated bitumen (slurry
conditioning). Thus, in
the hot water process, both oil sand slurry
preparation and slurry conditioning occur in the tumbler.
The conditioned slurry is introduced into a separation vessel typically
operating at 55 to 80 C to recover the bitumen. One of the limitations of
the hot water process is that, in general, such a tumbler based plant is at a
fixed location, ideally, one where large amounts of hot water/steam can be
produced.
The hot water process generally produces good bitumen recoveries
for all grades of oil sand. However, the thermal energy requirement per
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tonne of oil sand processed is very high. In particular, thermal energy is
required to heat the process water, for steam production and for heating
the flood water. Thus, the hot water process may only be practiced at
particular mine sites due to such limitations.
Another bitumen extraction process, which is disclosed in Canadian
Patent No. 2,029,795 and United States Patent No. 5,039,227, involves the
use of a pipeline to condition oil sand slurry. In this process, heated water
(typically at 95 C) is mixed with the dry as-mined oil sand at the mine site
in
predetermined portions using a device known as a "cyclofeeder", to form an
aerated slurry having a temperature in the range of 40-70 C, preferably
about 50 C (slurry preparation). The oil sand slurry is then conditioned
through several kilometres of pipeline (slurry conditioning) and transported
to an extraction plant where bitumen separation occurs typically at 55 C in
a separation vessel. This extraction process is referred to herein as the
"warm slurry process".
Because of the use of a hydrotransport pipeline to condition the oil
sand slurry, the warm slurry process allows for more flexibility, e.g., the
mine site may be more remotely located from a bitumen separation plant
where bitumen froth is produced from the conditioned oil sand slurry.
Furthermore, in warm slurry extraction, the slurry preparation unit is
generally relocatable and can be moved when required. The
hydrotransport pipeline which is used for conditioning can also be moved
when required.
Thus, in the warm slurry process, the pumping of the slurry through
a pipeline, over a certain distance, allows the slurry to be conditioned at a
lower temperature of about 50 to 55 C. With increased conditioning time
(i.e., typically 10 minutes or greater) in the pipeline, this process does not
compromise conditioning and bitumen recovery. Further, this process
allows the slurry preparation at the mine site and the bitumen separation at
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the bitumen separation plant, thereby reducing the requirement of dry oil
sand transportation. Hence, the warm slurry process generally has a
reduced carbon footprint and a reduced energy requirement.
In some instances, for example, at very remote mine sites where
access to thermal energy is limited, it is desirable to reduce the thermal
energy requirement per tonne of oil sand even more. Thus, an even lower
energy consuming bitumen extraction process was developed, which is
disclosed in Canadian Patent Nos. 2,217,623 and 2,506,398, and which is
hereinafter referred to as the "low energy process", i.e., a process where
slurry preparation and conditioning typically results in an oil sand slurry
having a temperature in the range of about 40-55 C. The low energy
process involves mixing the mined oil sand with water having a
temperature of about 75-85 C in predetermined proportions in a mix box
located near the mine site to produce a slurry containing entrained air and
having a controlled density in the range of 1.5 to 1.6 g/cc. The slurry is
then pumped through a pipeline to condition and transport the slurry (slurry
conditioning). The separation of bitumen from the conditioned slurry
typically occurs at about 35 C.
As mentioned, this process is particularly useful for mine locations
where there is limited access to hot water and steam and, in particular, at
remote mine locations. Because hot water is heated locally, i.e., requiring
a power generation system, a mine site can be located far away from the
base plant where bitumen froth cleaning and upgrading take place.
It is understood that other slurry preparation units can be used, such
as the unit described in Canadian Patent Application No. 2,480,122. When
using this slurry preparation unit, little or no rejects will be produced
during
slurry preparation. The slurry preparation unit comprises a series of roll
crushers spread vertically throughout a portion of a slurry preparation
tower. The slurry preparation tower typically uses gravity to move the oil
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sand through the tower. Typically, each roll crusher is made up of a
number of crusher rolls spaced a certain distance apart to reduce the size
of large pieces of oil sand before the lumps of oil sand drop through the
crusher rolls to the next roller crusher beneath or at the bottom of the
slurry
preparation tower. Each successively lower roll crusher reduces the lumps
of oil sand even smaller until the oil sand is fine enough to form a pumpable
oil sand slurry.
At the same time the oil sand passes through the different roll
crushers, heated water is added to the oil sand to form a slurry. Typically,
the stream of oil sand passing through the levels of roll crushers is sprayed
with the heated water, as it passes down the tower. The mixing of this oil
sand with the streams of hot water will form the eventual oil sand slurry,
which is typically received in a pump box for feeding the slurry to a pump
and pipeline system. This process reduces the bitumen loss to the rejects
due to the decreased amount of rejects, thus allowing more bitumen to be
recovered. This process is particularly useful when it is desirable to
produce minimal rejects and is hereinafter referred to as the "wet crushing
slurry preparation process".
In summary, selection of a particular slurry preparation process,
slurry conditioning process, and bitumen separation process will depend on
a number of factors, including the remoteness of the mine site, the ability
and cost to truck mined oil sand to the slurry preparation units and the
energy availability at the mine site.
SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a process and
process line for combining a number of different oil sand slurry preparation
and slurry conditioning processes (collectively referred to "slurry
preparation and conditioning processes") with a common bitumen
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separation process to provide a unified operation and allow the operator to
process oil sands in multiple mines in multiple locations more effectively,
efficiently, and economically. For example, having the ability to operate a
number of slurry preparation and conditioning processes at different
temperatures and at different mine sites allows an operator to utilize its
resource more efficiently by making maximum use of the heat available at
each mine site. However, there is still a need to be able to unify the
various slurry preparation and conditioning processes with common
bitumen separation processes to allow an operator to maximize bitumen
recovery.
In another aspect, there is a need to ensure that the downstream
bitumen processing (upgrading) capacity is fully utilized. Thus, there is a
need to unify bitumen froth treatment processes for the bitumen froth
products formed in bitumen separation processes.
In another aspect, there may be instances where there are multiple
trains of the same slurry preparation and conditioning process operating at
the same mine site and it is also desirable to unify these multiple trains
operating at a single mine site, in addition to unifying multiple mine sites.
In accordance with one aspect of the invention, a process is
provided for extracting bitumen from oil sand, comprising:
= preparing a first conditioned oil sand slurry at a first location using a
first slurry preparation and conditioning process;
= preparing a second conditioned oil sand slurry at a second location
using a second slurry preparation and conditioning process;
= combining the first conditioned oil sand slurry and the second
conditioned oil sand slurry in at least one slurry distributor to
produce a combined oil sand slurry; and
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= distributing the combined oil sand slurry to at least one separation
vessel to produce bitumen froth.
In one embodiment, the combined oil sand slurry is distributed to at
least two separation vessels and the bitumen froths from the at least two
separation vessels are combined in at least one froth storage tank for
further treatment. In one embodiment, the separation vessel is a gravity
separation vessel.
In one embodiment, the first location and the second location are at
a single mine site. In another embodiment, the first location and the
second location are at different mine sites.
In one embodiment, the first slurry preparation and conditioning
process and the second slurry preparation and conditioning process are the
same. In another embodiment, the first slurry preparation and conditioning
process and the second slurry preparation and conditioning process are
different.
In one embodiment, bitumen froth is deaerated prior to storage in at
least one froth storage tank. In one embodiment, the bitumen froth in the at
least one froth storage tank is subjected to further treatment to reduce the
solids and water content therein. In one embodiment, the treatment
comprises naphtha froth treatment. In another embodiment, the treatment
comprises paraffinic froth treatment.
In accordance with another aspect of the invention, a process is
provided for operating multiple oil sand mine sites for extracting bitumen
from oil sand, comprising:
= preparing a first conditioned oil sand slurry at a first mine site using a
first slurry preparation and conditioning process and subjecting the
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first conditioned oil sand slurry to a first bitumen separation process
to produce a first bitumen froth;
= preparing a second conditioned oil sand slurry at a second mine site
using a second slurry preparation and conditioning process and
subjecting the second conditioned oil sand slurry to a second
bitumen separation process to produce a second bitumen froth;
= combining the first bitumen froth and the second bitumen froth in at
least one froth storage tank to produce a combined bitumen froth;
and
= subjecting the combined bitumen froth to further treatment to reduce
the solids and water content therein.
In one embodiment, the first bitumen froth and the second bitumen
froth are deaerated prior to combining them in the at least one froth storage
tank. In one
embodiment, the first bitumen froth is heated prior to
combining it with the second bitumen froth. In one embodiment, the first
mine site is remote from the second mine site and the first bitumen froth is
transported to the second mine site by means of a froth pipeline.
In accordance with another aspect of the invention, a process is
provided for operating multiple oil sand mine sites for extracting bitumen
from oil sand, comprising:
= preparing a first conditioned oil sand slurry at a first mine site using
a
first slurry preparation and conditioning process and subjecting the
first conditioned oil sand slurry to a first bitumen separation process
to produce a first bitumen froth;
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= transporting the first bitumen froth to a second mine site by means of
a froth pipeline and combining the first bitumen froth with oil sand
ore mined at the second mine site and water; and
= preparing a second conditioned oil sand slurry from the combined
first bitumen froth, the oil sand ore mined at the second mine site
and water using a second slurry preparation and conditioning
process and subjecting the second conditioned oil sand slurry to a
second bitumen separation process to produce a second bitumen
froth.
In one embodiment, the combined second slurry preparation and
conditioning process and second bitumen separation process is a hot water
process. In another embodiment, the combined first slurry preparation and
conditioning process and the first bitumen separation process is a low
energy process.
BRIEF DESCRIPTION OF THE DRAWINGS
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.
FIG. 1 is a schematic of two different slurry preparation and
conditioning processes which are combined into a unified operation by a
common bitumen separation process in accordance with an embodiment of
the invention.
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FIG. 2 is a schematic of a bitumen froth treatment process useful in
the present invention.
FIG. 3 is a schematic of a combined slurry preparation and
conditioning process and bitumen separation process where the bitumen
froth produced can be combined with FIG. 1.
FIG. 4 is a block diagram showing the unification of three separate
trains of the slurry preparation and conditioning process and the bitumen
separation process, as shown in FIG. 3, with the processes of FIG. 1.
FIG. 5A, FIG. 5B, and FIG. 50 are a top view, front view and side
view, respectively, of an embodiment of a slurry distributor useful in the
present invention.
FIG. 6A and FIG. 6B are a top view and side view, respectively, of
another embodiment of a slurry distributor useful in the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention is exemplified by the following description and
examples.
A schematic of two different slurry preparation and conditioning
process trains, train 10 and train 20, operating at two different mine sites
that are integrated according to the present invention is shown in FIG. 1.
Train 10 depicts a remote slurry preparation and conditioning process,
which uses hydrotransport to condition oil sand slurry at ¨50 C (as
described in the warm slurry process). Train 20 depicts a slurry
preparation and conditioning process where oil sand slurry is conditioned in
a tumbler at ¨80 C (as described in the hot water process). While the two
slurry preparation and conditioning process trains operate at different mine
sites or different parts of the same mine, the conditioned oil sand slurries
produced at each site are combined allowing bitumen separation to occur
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at a single bitumen extraction plant, as will be described in more detail
below.
Train 10 comprises mined oil sand being delivered by trucks 12 to a
hopper 14 having an apron feeder 16 therebelow for feeding mined oil sand
to a double roll crusher 18 to produce pre-crushed oil sand. Surge feed
conveyor 26 delivers pre-crushed oil sand to surge facility 22 comprising
surge bin 28 and surge apron feeders 30 therebelow. Air 24 is injected into
surge bin 28 to prevent the oil sand from plugging.
The surge apron feeders 30 feed the pre-crushed oil sand to
cyclofeeder conveyer 32, which, in turn, delivers the oil sand to cyclofeeder
vessel 34 where the oil sand and water 36 are mixed to form oil sand slurry
40. Oil sand slurry 40 is then screened in screen 38 and screened oil sand
slurry 41 is transferred to pump box 42. The cyclofeeder system is
described in U.S. Pat. No. 5,039,227. Optionally, oversize lumps from
screens 38 are sent to secondary reprocessing (not shown). Oil sand
slurry 45 is then conditioned by pumping the slurry through a
hydrotransport pipeline 46, from which conditioned oil sand slurry 48 is
delivered to slurry distribution vessel 50 (also referred to herein as
"superpot"). A portion of oil sand slurry 44 can be recycled back to
cyclofeeder 34.
Train 20 comprises tumbler oil sand feed 13 being delivered by truck
11 and fed into tumbler 19. Tumbler hot water 15, caustic 17 (e.g., sodium
hydroxide) and steam 21 are also added to tumbler 19 where the oil sand is
mixed with the water to form a conditioned oil sand slurry. Residence time
of the slurry in the tumbler is generally around 2.0 to 4.0 minutes. The
slurry is then screened through reject screens 25 and rejects 27 are
discarded. Screened conditioned oil sand slurry 29 is then transferred to a
pumpbox 33 where additional water 31 may be added. The slurry 35 is then
pumped to slurry distribution vessel 50.
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=
Distribution vessel 50 is designed to mix the incoming flows, slurry
48 and slurry 35, to give a homogeneous slurry for further distribution. In
one embodiment, slurry distribution vessel 50 is a passive vessel, meaning
that no impellers are used. Hence, at this point, trains 10 and 20 are
unified and a homogeneous slurry is formed so that bitumen separation can
take place at a common bitumen separation plant to produce a more
consistent quality of bitumen froth.
In one embodiment, the bitumen separation plant comprises at least
one primary separation vessel, or "PSV". A PSV is generally a large,
conical-bottomed, cylindrical vessel. In the embodiment shown in FIG. 1,
slurry is distributed by the slurry distribution vessel 50 to two PSVs 54, 54'
via slurry streams 52, 52'. The slurry 52, 52' is retained in the PSV 54, 54'
under quiescent conditions for a prescribed retention period. During this
period, the aerated bitumen rises and forms a froth layer, which overflows
the top lip of the vessel and is conveyed away in a launder to produce
bitumen froth 60, 60'. The sand grains sink and are concentrated in the
conical bottom--they leave the bottom of the vessel as a wet tailings stream
56, 56'. Middlings 58, 58', a mixture containing fine solids and bitumen,
extend between the froth and sand layers.
Some or all of tailings stream 56 and middlings 58, 58' are
withdrawn, combined and sent to a secondary flotation process carried out
in a deep cone vessel 61 wherein air is sparged into the vessel to assist
with flotation of remaining bitumen. This vessel is commonly referred to as
a tailings oil recovery vessel, or TOR vessel. The lean bitumen froth 64
recovered from the TOR vessel 61 is stored in a lean froth tank 66 and the
lean bitumen froth 64 may be recycled to the PSV feed. The TOR
middlings 68 may be recycled to the TOR vessel 61 through at least one
aeration down pipe 70. TOR underflow 72 is deposited into tailings
distributor 62, together with tailings streams 56, 56' from PSVs 54 and 54',
respectively. It is understood, however, that other bitumen separation
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processes can be used in the present invention to unify separate mining
sites. It is also understood that a bitumen separation process can be
comprised of multiple pieces of equipment, for example, multiple primary
separation vessels, and multiple tailings oil recovery vessels.
PSV 54 bitumen froth 60 is then deaerated in steam deaerator 74
where steam 76 is added to remove air present in the bitumen froth.
Similarly, PSV 54' bitumen froth 60' is deaerated in steam deaerator 74'
where steam 76' is added. Deaerated bitumen froth 78 from steam
deaerator 74' is added to steam deaerator 74 and a final deaerated
bitumen froth product 80 is stored in at least one froth storage tank 82 for
further treatment. A typical deaerated bitumen froth comprises about 60
wt% bitumen, 30 wt% water and 10 wt% solids.
Currently, two different types of froth treatment processes are
commercially employed; naphthenic froth treatment, which uses a naphtha
diluent typically obtained from the downstream coking of bitumen, and
paraffinic froth treatment, which uses a paraffinic diluent composed of a
mixture of hexanes and pentanes. Froth treatment involves the removal of
water and solids still present in the deaerated bitumen froth to produce a
bitumen product for upgrading.
A naphthenic froth treatment process useful in the present invention
is shown in FIG. 2. It is understood, however, that other froth treatment
processes can be used. Bitumen froth 84 stored in froth tank 82 can be
split into two separate streams, streams 86, 86'. Naphtha 88, generally at
a diluent/bitumen ratio (wt./wt.) of about 0.4-1.0, preferably, around 0.7,
and a demulsifier 90 are added to bitumen froth stream 86 to form a diluted
froth stream 91 which is then subjected to separation in an inclined plate
settler 92 (IFS). The IPS 92 acts like a scalping unit to produce an
overflow 83 of diluted bitumen and an underflow 96 comprising water,
solids and residual bitumen.
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Overflow 83 is then filtered in a filter 93 such as a Cuno filter to
remove oversize debris still present in the diluted bitumen 83. Filtered
diluted bitumen 85 is further treated in a disc centrifuge 95 which separates
the diluted bitumen from the residual water (and fine clays) still present. A
disc machine separates the hydrocarbon from the water in a rotating bowl
operating with continuous discharge at a very high rotational speed.
Sufficient centrifugal force is generated to separate small water droplets, of
particle sizes as small as 2 pm to 5 pm, from the diluted bitumen.
The final diluted bitumen product 87 typically comprises between
about 0.5 to 0.8 wt.% solids and 2.0-5.0 wt.% water and bitumen recovery
is about 98.5 %.
Deaerated bitumen froth stream 86' from froth tank 82 is also treated
with naphtha at a diluent/bitumen ratio (wt./wt.) of about 0.4-1.0,
preferably,
around 0.7. The underflow 96 from IFS 92 can be added to stream 86' in
order to recover any residual bitumen present in this underflow stream.
The diluted bitumen froth is then treated in a decanter (scroll) centrifuge 94
to remove coarse solids from naphtha diluted froth. Decanter centrifuges
are horizontal machines characterized by a rotating bowl and an internal
scroll that operates at a small differential speed relative to the bowl.
Naphtha-diluted froth containing solids is introduced into the centre of the
machine through a feed pipe. Centrifugal action forces the higher-density
solids towards the periphery of the bowl and the conveyer moves the solids
to discharge ports.
The solids 103 are then fed to a heavy phase tank 104. The diluted
bitumen 89 is further treated with a demulsifier 90, filtered in a filter 98
and
the filtered diluted bitumen 100 is further treated in a disc centrifuge 99.
The resultant diluted bitumen 101 is then treated, along with filtered diluted
bitumen stream 85, in disc centrifuge 95 which separates the diluted
bitumen from the residual water (and fine clays) still present to give final
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diluted bitumen stream 87. The solids 102 are also fed to heavy phase
tank 104. The solids 105 are then treated in a naphtha recovery unit 106
where naphtha 107 is separated from the froth treatment tailings 108.
Thus, despite slurry preparation and conditioning occurring at two
different mine sites using different slurry preparation and conditioning
processes, the blending of the conditioned oil sand slurries in the slurry
distributors (superpots) gives operational flexibility and improved bitumen
extraction and separation through slurry blending. Having different slurry
preparation and conditioning processes operating at different temperatures
allows the operator to utilize the resource more efficiently, by maximizing
use of the heat available at each mine site.
Further, the combination of bitumen extraction and froth treatment
allows the operator to process oil sands in multiple mines in multiple
locations. The pooling of bitumen froths in froth storage tanks maintains
production capacity of the froth treatment facilities to produce diluted
bitumen product. It also ensures that the downstream bitumen processing
capacity is fully utilized.
In some instances, particularly where mine sites are very remote, it
is more economical to transport bitumen froth rather than conditioned oil
sand slurry, as is the case above. In particular, froth transportation using
natural froth lubricity enables slurry preparation and conditioning and
bitumen separation to occur remotely and the bitumen froth to be
transported to a bitumen froth treatment plant at a different location, which
increases production and maximizes the use of processing equipment.
This aspect of the present invention will be discussed in more detail
following.
In some embodiments, a third bitumen extraction process, for
example, a low energy process, can be operating at yet another mine site.
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The low energy process can be tied into the process shown in FIG. 1 as
follows. FIG. 3 shows a typical low energy process 300 which can be used
at mine sites where heat is less available. In the low energy process, oil
sand ore is surface mined using shovels and transported by trucks to be
pre-crushed in a primary crusher 330, preferably a double roll crusher.
Pre-crushed oil sand is then conveyed by conveyor 332 and stock piled
until further use (surge pile 334). The pre-crushed oil sand is then
conveyed by conveyor 336 to a mix box 338 where hot slurry water and
caustic (e.g., sodium hydroxide) is added to form a slurry. Mix box 338
comprises a plurality of mixing shelves 340 to mix the oil sand with hot
slurry water to produce oil sand slurry. Oil sand slurry 354 leaves the
bottom outlet 356 of the mix box 338 as unscreened slurry 354 and is then
screened using screen 342 where additional hot slurry water can be added.
The screened slurry is then deposited in pump box 352.
Screened rejects 344 are fed to an impact crusher 346 and
screened again through screen 348. Oversize rejects 358 are discarded but
screened material enters pump box 350, where more water is added and
then oil sand slurry is pumped into pump box 352. The oil sand slurry in
pump box 352 is then pumped via pumps 360 through a hydrotransport
pipeline 362 for conditioning to produce conditioned oil sand slurry.
If the mine site is very remote, i.e., it is too far away from an existing
bitumen separation plant to make it economical to transport the conditioned
oil sand slurry to the existing plant, a bitumen separation plant is also
provided at or near the remote mine site. Conditioned oil sand slurry is
transferred to slurry distributor 369 (superpot) and then pumped via pump
364 through a second section 366 of pipeline where cold flood water is
added. Diluted slurry is then introduced into primary separation vessel
(PSV) 368 and retained under quiescent conditions, to allow the solids to
settle and the bitumen froth to float to the top. A froth underwash of hot
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water is added directly beneath the layer of bitumen froth to aid in heating
the froth and improving froth quality.
Thus, a bitumen froth layer, a middlings layer and a solids layer are
formed in the primary separation vessel 368. Middlings from primary
separation vessel 368 are removed and undergo flotation in flotation cells
370 to produce secondary froth. Secondary froth is recycled back to the
primary separation vessel 368. Tailings, comprising the solids, water, etc.
that collects at the bottom of the primary separation vessel 368 are
removed and deposited into tailings pond 376 or sent to a composite
tailings plant.
Bitumen froth, or primary froth, is removed from the top of the
primary separation vessel 368 and then deaerated in froth deaerator 372.
Once deaerated, the primary froth can be retained in froth tank 374. The
deaerated bitumen froth stored in froth tank 374 can then be pumped using
froth booster pumps via froth pipeline 378. Because the deaerated bitumen
froth contains about 20 to 40% by volume water and the water contains
colloidal-size particles such as clay, deaerated bitumen froth can be
transported for long distances through froth pipeline 378 by establishing
self-lubricated core-annular flow. Water can be added to promote the
transport of froth in the pipeline if insufficient water is present in the
deaerated froth. Core-annular flow is described in more detail in U.S. Pat.
No. 5,988,198.
In one embodiment, a portion of the deaerated bitumen froth in froth
tank 374, referred to in FIG. 3 as deaerated bitumen froth 382, can be
transported to another mine site and used in slurry preparation. For
example, deaerated bitumen froth 382 can be fed directly into a hot water
process, such as hot water process 20 shown in FIG. 1, to enhance the
froth quality and to enrich a bitumen ore feed which may be a poor
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processing oil sand ore. As illustrated in more detail in FIG. 1, the
deaerated bitumen froth 382 can be added to tumbler 19.
In addition, or, in the alternative, a portion of deaerated bitumen
froth, referred to in FIG. 3 as deaerated bitumen froth 380, can be fed to
froth storage tanks 82 (also shown in FIG. 1), which froth storage tanks
may also store bitumen froth from hot water process 20 and warm slurry
process 10, as shown in FIG. 1. Optionally, deaerated bitumen froth 380
can be heated in heater 400 prior to storage in storage tank 82. In one
embodiment, deaerated bitumen froth is heated to a temperature greater
than 35 C. In another embodiment, the deaerated bitumen froth 380 is
heated to a temperature greater than 50 C.
Thus, in this embodiment, three different bitumen extraction
processes have been linked together to form a single, uniform froth product
for further treatment and upgrading.
In the low energy process, the temperature of the hot slurry water
used in the slurry mixing step is generally about 75 C. to about 85 C.,
which, when mixed with the oil sand, results in an oil sand slurry having a
temperature greater than 40 C., preferably greater than 43 C., and more
preferably in the range of about 40 C. to about 55 C., and a density in the
range of about 1.5 g/cc to about 1.6 g/cc. Caustic soda (NaOH) and other
processing aids can be also added at this step, if necessary or desired.
The conditioning step can be performed either by pumping the oil
sand slurry through a pipeline of sufficient length (e.g., typically greater
than about 2.5 km) so that liberation of bitumen from sand and subsequent
conditioning and aeration of bitumen both require sufficient time to occur.
Preferably, conditioning time is about 10 minutes or more when using a
pipeline of sufficient length.
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The cold flood water temperature used in the flooding step generally
ranges between 5 C. and 25 C., which results in a flooded or diluted
slurry having a temperature of about 25 C. to about 40 C. and a density
of about 1.4 g/cc to about 1.5 g/cc. More preferably, the diluted slurry will
have a density of about 1.4 g/cc to about 1.45 g/cc and a temperature in
the range of about 30 C. to about 40 C., preferably, a temperature of
about 35 C. Use of cold flood water for flooding eliminates the need to
heat water or import heated water from other sources, and readily
available, lower quality pond water can be used.
In one embodiment, at least two trains of low energy process may
be operating at a single mine site to maximize separation (extraction)
equipment usage. FIG. 4 illustrates three low energy slurry preparation
and conditioning process trains, Train 1, Train 2 and Train 3, and two low
energy bitumen separation trains, which are all integrated to produce a
bitumen froth product. In particular, each of Trains 1,2, and 3 represents a
low energy slurry preparation and slurry conditioning process as illustrated
in FIG. 3 and described above. Conditioned oil sand slurry produced in
each of Train 1, Train 2 and Train 3 is pooled in slurry distributor 369 (also
referred to as "superpot" or SP). It is understood, however, that all three
trains need not be operating at all times and various bypass systems can
be used when one or two trains is/are not being operated. The pooled
conditioned oil sand slurry can then be subjected to bitumen separation, for
example, flotation in at least one primary separation vessel 368, as
illustrated in FIG. 3 and described above. However, it is understood that
more than one primary separation vessel can be used. FIG. 4 illustrates
two primary separation vessels being used, 368, 368'.
The bitumen froths produced from primary separation vessel 368
and primary separation vessel 368' are deaerated by steam, pooled and
pumped through froth pipeline 378. A portion of the deaerated bitumen
froth, 380, can be optionally heated using heater 400, and then stored in
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froth storage tank 82. Another portion of the deaerated bitumen froth, 382,
can be added to hot water process 20 as described above.
FIG. 4 also illustrates how hot water slurry preparation and
conditioning process 20 and warm slurry preparation and conditioning
process 10 share a common bitumen separation process and, in addition,
are integrated with low energy extraction process to produce a single
deaerated bitumen froth product which can be stored in froth storage tank
82. Conditioned oil sand slurries 35, 48 are pooled into slurry distributor
50, subjected to flotation in primary separation vessels 54, 54', and the
bitumen froths deaerated and pooled as deaerated bitumen froth product
80 and stored in froth storage tank 82 for further treatment and upgrading.
Thus, in FIG. 4 it can been seen that three different slurry preparation and
conditioning processes and two different bitumen separation processes can
be used at three distinct mine sites but can also be integrated to produce a
single, uniform bitumen froth product for further treatment and upgrading.
FIG. 5A, FIG. 5B and FIG. 5C are illustrations of a top view, front
view and side view of a slurry distributor useful in the present invention. In
general, slurry distributors are designed to mix incoming feed streams (e.g.,
conditioned slurries) to provide an even feed flow, with similar composition
(i.e., air, solids, bitumen and water), at similar temperatures, to operating
bitumen separation vessels such as primary separation vessels. Thus, for
example, if one stream is warmer than the other two streams, the heat will
be evenly distributed, which will result in better overall bitumen recovery.
Slurry distributor 500, shown in FIGS. 5A, 5B and 5C, is particularly
useful when there are three feed lines for two outlets, as shown in FIG. 4
for the three trains, Train 1, Train 2 and Train 3. Slurry distributor 500
comprises a cylindrical body 510 having a inverted frustoconical bottom
portion 516. Slurry distributor 500 further comprises three inlet pipes 502,
504 and 506 located at or near the top 518 of the slurry distributor 500.
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Generally, slurry distributor 500 is a closed top vessel having a large vent
(not shown). The closed top prevents excessive steaming/heat loss and
splashing from the jet mix zone, which prevents winter ice build up on
vessel walls, pipes, instruments, and ramp/handle rails.
Optionally, each inlet pipe may terminate with a miter (not shown).
Outer inlet pipes 502 and 506 are angled toward the central inlet pipe 504.
Three conditioned oil sand slurries, which may come from three separate
hydrotransport feed lines (not shown), will each be fed into one of the inlet
pipes. Located at or near the closed bottom 520 of slurry distributor 500
are two outlet pipes 512 and 514, which outlets may be substantially
perpendicular to central inlet pipe 504. Outlet pipes 512 and 514 distribute
mixed conditioned slurry to two bitumen separation vessels, for example,
two primary separation vessels (not shown), via attached outlet feed lines
(not shown).
Slurry distributor 500 may be installed at ground level and the outlet
streams of conditioned slurry may be pumped to the primary separation
vessels' feedwells. The configuration of the inlet pipes 502, 504, 506
allows for more thorough mixing of the three conditioned slurry feed
streams and having the inlet array rotated 90 degrees from the two outlets
also increases mixing of the three conditioned slurries. Thus, a
substantially homogeneous conditioned slurry product is formed, which
contributes to a more consistent bitumen froth formation in the two primary
separation vessels. It is understood, however, that not all incoming feed
lines, which are attached to the inlet pipes, need to be operating at all
times. Slurry
distributor 500 allows the operator the flexibility to
operate/switch incoming feed lines and outlet feed lines to the primary
separation vessels.
FIG. 6A and FIG. 6B are illustrations of a top view and side view,
respectively, of another slurry distributor useful in the present invention.
In
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this embodiment, slurry distributor 600 comprises an substantially
cylindrical upper portion 610, a substantially frustoconical mid section 611,
and a substantially cylindrical bottom section 616, where the diameter of
the bottom section 616 is substantially greater than the diameter of the
upper portion 610. Inside the slurry distributor 600 is a substantially
cylindrical baffle 624.
In this embodiment, there are six inlet pipes 601, 602, 603, 604, 605
and 606, located near the top 618 of the slurry distributor 600 extending
substantially perpendicularly from the cylindrical upper portion 610. Slurry
distributor 600 is also a closed top vessel with a vent to prevent excessive
moisture venting inside the building and heating the building up, as well as
contributing to corrosion. There are also six outlet pipes 612, 613, 614,
621, 622 and 623 located near the closed bottom 620 of the slurry
distributor 600 extending substantially perpendicularly from the cylindrical
bottom section 616.
Slurry distributor 600 may be installed above six primary separation
vessels and the mixed conditioned oil sand slurry flows by gravity through
outlet feed lines (not shown) which are connected to each outlet pipe of the
slurry distributor 600 and feedwells of corresponding primary separation
vessels. The flow to the primary separation vessels may be controlled by
means of valves. The cylindrical baffle 624, which is located inside the
slurry distributor 600, reduces violent mixing and short circuiting of
incoming flows at low operating levels, which would result in an adverse
flow distribution between the discharge ports. Thus, the presence of the
skirt baffle significantly reduces the turbulent eddy scale as well as the
intensity in the distributor body, but especially in the annular space and at
the discharge ports.
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