Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02733881 2011-03-10
INTEGRATING OLEOPHILIC SIEVES INTO EXISTING
COMMERCIAL FROTH FLOTATION OIL SANDS
PLANTS.
RELATED APPLICATIONS
This application is related to Canadian Patent Application Number 2,638,596
entitled: "ENDLESS CABLE SYSTEM AND ASSOCIATED METHODS" filed
2008/08/06, Application Number 2,661,579 entitled: "HELICAL CONDUIT
HYDROCYCLONE METHODS" filed 2009/04/09, Application Number 2,704,175
entitled "REMOVING HYDROPHILIC MINERALS FROM BITUMEN PRODUCTS
filed 2011/11/18 and to several other granted patents and patent applications
of the same
inventor that are related to a lesser degree to the instant application, and
are on file with
the Canadian patent office.
BACKGROUND OF THE INVENTION
The first commercial mined oil sands plant was constructed in 1967 on the
banks
of the Athabasca river about 50 kilometres North of the City of Fort McMurray.
This
river flows North and joins the McKenzie river that flows into the Arctic
Ocean and
carries with it any debris flowing into the Athabasca river. Every barrel of
oil produced
from the oil sands generates several barrels of toxic effluent that may not be
returned to
the river but are stored in holding ponds that continue to create major
concerns for the
environment and has been a topic of heated discussion, with calls in
newspapers and
magazines for the termination of oil sands development in Alberta. Only very
recently
has the oil sands industry taken notice of those calls and are now striving to
reduce the
environmental impact of oil sands development. The present invention
represents
independent technology that has been developed to overcome tailings pond
problems
which are characterized by the accumulation in ponds of toxic fluid tailings
that will not
dewater quickly but are thought to release toxic fluid into the surrounding
ground water
table.
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Figure 1 is a flow diagram of one commercial oil sands plant that illustrates
the
complexity of current commercial bitumen extraction from mined oil sands.
Every
commercial oil sands plant uses a slightly different flow diagram to optimize
bitumen
recovery. Some use tailings oil recovery vessels (TORV) and others use sub-
aeration
froth flotation cells to optimize bitumen recovery but they all produce toxic
tailings
effluents that flow to tailings ponds where sand and gravel drop out on the
shore and the
remaining fluid tailings report to the sedimentation pool of each tailings
pond.
Figure 2 is a comparison illustration of efforts of the past that were piloted
to
clean up the fluid tailings of a commercial oil sand tailings pond. The top of
the Figure
illustrates a flow diagram in which an effort was made to process aged fluid
tailings by
means of bitumen froth flotation. The bottom of the Figure illustrates a flow
diagram in
which an oleophilic sieve was used for the same purpose. The table besides the
illustrations compares the effectiveness of each method. A very revealing
result of this
comparison is that the oleophilic sieve process required only one processing
step of about
3 minute duration whilst bitumen froth flotation of fluid tailings required
four processing
steps and a total duration of 30 about minutes. As tabulated, not only was the
Sieve ten
times faster but it was simpler with superior performance. Current research by
the oil
sands industry continues to be devoted to allowing fluid tailings to mature,
so as to
recover as much of the tailings water as possible by long duration compaction
in the
tailings ponds. After the compacted fluid tailings have reached a water
content of less
than 65%, pilot tests are then conducted by industry to mix the mature fluid
tailings with
chemicals and with dry sand to form a landscape that may support fauna, trees,
etc. In
contrast, the technology of the present inventor is mainly concentrated on
processing the
mined oil sand fluid streams before these have matured. Using that approach,
it is
anticipated that the time needed to remediate commercial mined oil sands
tailings ponds
will be much shorter and the bitumen products recovered will be fresher.
SUMMARY OF THE INVENTION
Current mined oil sands plants use technology that was developed prior to
1967.
It was gradually improved but still uses the concept of aerating bitumen to
cause it to rise
to the top of separation vessels. The bitumen droplets have to negotiate a
difficult upward
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path against downward flowing solids, gravel, sand, silt and clay, in settling
aqueous
slurry. In many cases, caustic soda is needed to thin the slurry for better
flow, and to
produce detergents by methods like saponification, which help to disengage
fines from
bitumen surfaces. It takes a long time for sufficient bitumen to rise to the
top of
separation vessels to make commercial oil sand extraction profitable. However,
vast
amounts of money have been invested in each existing commercial mined oil
sands plant
and it would not make much economic sense to suddenly replace all the existing
commercial plant equipment with new technology equipment. Perhaps, after new
technology has been proven without doubt to be commercially superior, only
then, will it
make sense for new oil sands plant to use all new equipment to optimize the
operation of
producing bitumen from mined oil sand ore.
The oleophilic sieve, however, is well suited for optimizing the existing
commercial plants since it is a water based process that can use the front end
of any
existing mined oil sand extraction plant without major changes. It can use the
same
mining methods, the same oil sand and water slurry preparation methods and the
same
primary separation vessel (PSV) to produce primary bitumen froth. Beyond the
PSV,
several oleophilic sieve in series or parallel may be used to replace the TORV
or the sub-
earation cells to recover secondary bitumen from the middlings of that PSV. In
this
manner the PSV may serve to remove gravel and coarse sand from the oil sand
slurry and
cream off high grade bitumen froth by bitumen froth flotation in which a
premium
bitumen froth, that is low in minerals content, is skimmed off the top. This
primary froth
will be low in minerals content because the residence time in the PSV will be
reduced by
the present invention as compared with the current commercial residence time,
so that
only the large and minerals free bitumen droplets have enough time to rise to
the top of
the PSV to be skimmed off and recovered. The middlings are then processed by
oleophilic sieves to achieve secondary bitumen recovery. This approach not
only will
increase overall bitumen recovery and bitumen product quality but it also will
speed up
oil sand extraction in a major way.
Normally it takes a minimum of 45 minutes of processing time in a PSV for
primary bitumen recovery and a minimum of another 45 minutes for secondary
bitumen
recovery in the TORV (Fig. 1) or in sub-aeration cells to achieve the desired
separation of
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mined oil sand slurry. The middlings from a PSV are similar in composition to
tailings
pond fluid tailings except that the bitumen content normally is higher. For
reasons of this
similarity, the speed of separating middlings by oleophilic sieves will not
differ greatly
from the speed of separating tailings pond fluid tailings. The speed of
separation of fluid
tailings by oleophilic sieves was determined by the inventor when processing
an average
of 2.0 cubic meters per hour of fluid tailings through an oleophilic sieve
drum (See Fig 2)
that was 95 mm. long and 1.108 m. in diameter rotating at 3 RPM. Accordingly
the drum
volume in cubic metres was (7r)(0.095)(1.108)(1.108)/4 =0.0916 m3 ,and
dividing 0.0916
m3 by 2 m3/hr results in a residence time of 0.0458 hours, or 2.75 minutes.
But that is a
conservative calculation since the drum was partly filled with balls that
tumble in the
drum and these balls reduced the effective void volume of the drum for
processing
feedstock. For example when the balls occupy 40 percent of the drum volume,
the
residence time then becomes (2.75)(0.6) or 1.65 minutes. For middlings
processing the
optimum drum ball volume is a function of many variables, including drum
temperature
and drum RPM, and has not yet been accurately determined. However it is
reasonable to
assume that it will be less than 3 minutes. Comparing a processing time of 45
minutes
for a TORV or subaeration cells with a processing time of 3 minutes for an
oleophilic
sieve makes it obvious that placing several oleophilic sieves in series would
not create a
problem in a commercial oil sands extraction plant, but would speed up oil
sand slurry
processing in a major way.
BRIEF DESCRIPTION OF THE FIGURES
FIG. I is a flow diagram of one typical commercial mined oil sand separation
plant.
FIG. 2 illustrates the difference between a flow diagram for bitumen froth
flotation, to separate tailings pond fluid tailings, versus using an oleophlic
sieve for that
that same purpose.
FIG. 3 illustrates a modern, newly developed concept of an oleophilic sieve,
and
the application of that concept to allow for the efficient use of a revolving
drum
containing medium density balls.
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FIG. 4 illustrates the use of a modern oleophilic sieve to process middlings
from a
PSV to speed up oil sand slurry separation.
FIG. 5 illustrates modifications that may be made to a PSV to optimize its use
as a
front end for one or more modern oleophilic sieves.
FIG. 6 illustrates the use of a modern oleophilic sieve for washing one or
more
bitumen products with water to remove hydrophilic mineral particles.
FIG. 7 illustrates the use of a modem oleophilic sieve to process conventional
oil
sand tailings when these arrive at a tailings pond to recover residual
bitumen.
DETAILED DESCRIPTION
Before the present invention is disclosed and described, it is to be
understood that
this invention is not limited to the particular structures, process steps, or
materials
disclosed herein, but is extended to equivalents thereof as would be
recognized by those
ordinarily skilled in the relevant arts. It should also be understood that
terminology
employed herein is used for the purpose of describing particular embodiments
only and is
not intended to be limiting.
Definitions:
In describing and claiming the present invention, the following terminology
will
be used in accordance with the definitions set forth below. Bold text is used
in this
section only to make it easier to find the definition descriptions.
As used herein, "ball-fill" of a bed of balls in a drum may be defined as the
volume of the bed of balls, including voids in and between the balls, divided
by the
internal drum volume. It may be expressed as a percentage of the drum interior
volume;
100% representing a bed that completely fills the drum.
As used herein, "cable wraps" refer to wraps of and endless cable. It also is
used
to refer to wraps of an endless rope. For example steel wire rope often is
referred to as
cable, and plastic rope, such as polypropylene rope, nylon rope or polyester
rope more
often is referred to as rope instead of cable. In these specifications, cable
and rope are
used interchangeably.
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As used herein, "modern oleophilic sieve" refers to a revolving apertured
endless
belt wall formed by adjacent wraps of one or more endless cables supported by
two
rotating supports. A modern Oleophilic sieve has a separation zone and a
bitumen
removal zone. Rotating support in the separation zone is an apertured
cylindrical drum
wall and rotating support in the bitumen removal zone is at least one roller.
Apertures of
the modern Oleophilic sieve are the void spaces between adjacent cable wraps.
As used herein, "old type oleophilic sieve" refers to a revolving apertured
endless
belt formed by a commercially available apertured mesh belt supported by two
rotating
supports. An old type oleophilic sieve has a separation zone and a bitumen
removal
zone. Rotating support in the separation zone is a perforated cylindrical drum
wall and
rotating support in the bitumen removal zone is in the form of several steam
heated
rollers which cause bitumen to drip from the mesh belt. Apertures of the old
type
oleophilic sieve are the mesh openings. Mesh belts have cross members and were
found
to unravel after long duration use, and fell apart. Replacing mesh belts or
hinge type
metal conveyor belts with adjacent wraps of endless cable or rope to improve
the process
was a later development. Old type oleophilic sieves and modern oleophilic
sieves were
inventions of the same inventor.
As used herein, "oleophilic" refers to bitumen adhesion to a surface or to
itself at
process temperature. A surface or a liquid is oleophilic when at the various
process
temperatures of the present invention it will adhere to bitumen, or bitumen
will adhere to
it. For example, when a surface it coated with light oil, bitumen will not
adhere to it
effectively, as the light oil will form a barrier that interferes with bitumen
adhesion.
Similarly when a surface is coated with bitumen that is at high temperature,
cold bitumen
will have some difficulty adhering to that high temperature bitumen because of
the low
viscosity of hot bitumen compared with the high viscosity of bitumen at
optimum
oleophilic sieve process temperature in the separation zone. Thus, in the
present
invention, oleophilic refers to a condition that can be influenced by
differences in
hydrocarbon composition and by differences in viscosity, and normally requires
that the
adhering surfaces are at approximately the same temperature as the bitumen
containing
mixture being processed in the various apparatus locations of an Oleophilic
sieve. In
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many cases metals and plastics are oleophilic with respect to bitumen,
especially when
pre-coated with a thin layer of bitumen and are close to process temperature.
As used herein, "oleophilic sieve" refers to either modem oleophilic sieve or
to
old type oleophilic sieve. It refers to method and/or apparatus for separating
bitumen
containing aqueous mixtures into bitumen phase and aqueous phase by means of a
revolving endless sieve. The sieve may be an endless belt or a cylindrical
drum wall,
both of which have apertures that allow aqueous phase of the mixture,
including mineral
particles suspended in the aqueous phase to pass through the apertures whilst
bitumen of
the mixture coming in contact with surfaces of the revolving sieve adheres to
said
surfaces in a separation zone. Instead of a mesh endless belt, the sieve may
also be
formed from multiple adjacent wraps of endless cable or endless rope to
resemble an
endless belt and this sieve may also be supported by a drum with aperture
cylindrical wall
to form a separation zone in which bitumen adheres to the cable wraps. At
least part of
the adhering bitumen phase is subsequently removed from the surfaces of the
sieve in a
bitumen removal zone. An oleophilic sieve may also use an apertured endless
mesh belt
in contact with at least part of a cylindrical drum wall that is perforated. A
sieve that uses
multiple adjacent wraps of endless cable normally uses a number of methods to
keep the
wraps properly aligned. However, unlike the problems of mesh belt tracking
alignment
between separation zone and bitumen removal zone, a sieve formed from adjacent
cable
wraps is easy to keep in tracking alignment. The bitumen phase removed from
the sieve
in a bitumen removal zone may contain mineral particles and water. The aqueous
phase
that has passed through the apertures of an oleophilic sieve may contain some
residual
bitumen that has passed through the apertures without adhering to the sieve
surfaces.
As used herein, "process temperature" refers to the temperature at which a
feedstock or a product is processed. In an Oleophlic Sieve apparatus there may
be two or
more process temperatures, for example, the process temperature of the
separation zone
and the process temperature of the bitumen removal zone. In some cases, sieve
cable
wraps may be cooled in a cooling zone between the bitumen removal zone and the
separation zone. In that case a third process temperatures may exist in an
oleophilic sieve
apparatus.
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EMBODIMENTS OF THE INVENTION
A typical commercial mined oil sands extraction plant is illustrated in Fig.
1. Oil
sand is mined by a very large electric shovel and conveyed by ore carrying
trucks to a
crusher hopper where the oil sand is crushed by rollers and is mixed with
water and
sodium hydroxide, or similar caustic processing aid, in a mixer or in a cyclo
feeder that
also entrains air in the mixture. From there the mixture is pumped through a
slurry
pipeline where turbulence and the process aid, along with warm or cool water
convert the
slurry into a well digested mixture, in which bitumen of the oil sand ore is
disengaged
from the sand grains and from rocks, gravel and part of the clay. In the older
commercial plants, rotating conditioning drums are still used instead of
slurry pipelines to
achieve the same desired result. Flood water is added to the slurry to dilute
it and make it
suitable for processing in a primary separation vessel (PSV) where the diluted
slurry
separates into three components, bitumen froth, middlings and tailings
(sometines called
bottoms). During separation, bitumen particles of the flooded slurry attach to
air bubbles
and causes bitumen to rise to the top of the PSV and become primary bitumen
froth
product. The bottoms may be pumped to a tailings pond or may be combined with
the
middlings for processing by a tailings oil recovery vessel (TORV) where
additional
bitumen is scavenged from the slurry stream. A hydrocyclone may be used to
scavenge
for additional bitumen before the tailings of the TORY are sent to a tailings
pond. The
process has a series of process loops to optimize the amount of bitumen
scavenged,
which bitumen eventually joins the froth product. These loops require
additional pumps
and piping and process control to optimize the process. In the drawing the
heavy lines
represent the flow lines that may remain when one or more oleophilic sieves
are used to
replace the TORY. The thin lines represent the flow lines that become obsolete
when this
replacement is put into effect and the TORV and hydrocyclone are removed
Other commercial mined oil sands extraction plants may use a number of sub-
aeration flotation cells, such as rougher flotation cells and scavenger
flotation cells (See
Fig. 2 for examples of these) instead of a TORY. In such plants, modern
oleophlic sieves
may be used to replace the sub-aeration cells.
Fig. 2 illustrates, by means of two illustrations, and a table beside each,
that in a
pilot plant, one oleophilic sieve was able to replace four froth flotation sub-
aeration
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bitumen recovery steps for processing tailings pond fluid tailing and yet
achieve higher
bitumen recovery. This was an important finding since fluid tailings are very
similar to
middlings, except that middlings normally contain a higher percentage of
bitumen.
A modem oleophlic sieve is illustrated in Fig. 3. Unlike the older patents of
the
inventor, this sieve is very different from older types of oleophilic sieves
that used mesh
belts for the sieving and required belt tracking control between separation
zone and
bitumen removal zone. A modem oleophilic sieve is described in detail in
Canadian
patent application Number 2,638,596 and in subsequent patents of the present
inventor.
Unlike the previous old oleophilic sieves, the improved modem oleophilic sieve
is much
stronger and longer lasting. Not only is it stronger, lasts longer, and sieves
better but
bitumen removal from the sieve has been dramatically improved. The concept is
illustrated in the insert in Fig. 3 at left and shows two rollers supporting
an endless cable
made from, for example, steel wire rope or polyester rope. A cable guide
directs the last
wrap of the endless cable or rope back to the opposite side of the rollers
just before it is in
danger of rolling off the grooved roller supports. The number of cable guides
used is the
same as the number of endless cables used to form multiple cable wraps on the
rollers, in
case more than one endless cable is used. The desired spacing between the
cable wraps is
flexible, and may be chosen to accomodate bitumen viscosity or other process
variables.
For separating middlings, bitumen may adhere to the wraps and may also bridge
the
space between the wraps.
The application of the modem oleophilic sieve concept is shown to the right in
Fig. 3. In this case one of the rollers has become a drum with aperture
cylindrical wall.
The drum is partly filled with a medium density bed of balls. A medium density
of the
bed of balls is achieved by using a mixture of, for example, 1.5 inch (40 mm)
heavy steel
griding balls and strong but light golf balls of approximately the same size.
In Fig. 3 the
balls are represented by shaded circles of exaggerated size and are not drawn
to scale
with respect to the much larger drum diameter. For optimum performance the bed
is
dense enough to cause the balls to revolve and tumble in the drum in the
presence of
bitumen. The colder the bitumen in the middlings, the higher the required
density of the
bed of balls; or the higher the concentration of steel balls needed with
respect to the
concentration of golf balls in the bed. Of course other balls may be used
instead of golf
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balls and instead of steel grinding balls. Balls may be developed to have a
metal core and
a thick rubber or plastic coating to achieve the desired average ball density.
Alternately
spherical "Jaeger" tower packings may be used instead of golf balls, provided
these are
made strong enough to stand up to abuse from metal balls in the same bed.
Ball-fill in the drum may be defined as the volume of the bed of balls,
including
voids in and between the balls, divided by the internal drum volume and may be
optimized for the middlings to be processed. For example, hollow balls may be
used as
well. Ball-fill may be expressed as a percentage of the drum interior volume;
100%
representing a bed that completely fills the drum. The torque required to turn
the drum
normally increases as the ball-fill increases from zero until the bed fills
about half of the
drum volume. After the ball-fill exceeds half the drum volume, the torque
required to
turn the drum may tend to reduce progressively. However the required torque
also is
influenced by the viscosity of the bitumen stripped from the middlings.
Heavier bearing
are required to support a drum that has a higher and heavier ball-fill.
However, the drum
of Fig. 3 should not be compared with a ball mill that requires very heavy
construction
and supports. The bed of balls in Fig. 3 is just dense enough to allow
revolving and
tumbling of the bed of balls in the presence of middlings to massage the
middlings and
captured bitumen at the selected internal drum temperature.
Fig. 3 is only a sectional drawing of the drum, showing its internals.
Normally
the drum is mounted in bearings supported by at least one shaft at one end
wall of the
drum, and that shaftt may be driven. In that case one drum end wall is closed
to allow
rotating support of the drum at one end by a shaft attached to that first end
wall, with the
shaft being mounted in a bearing. The second end wall of the drum may also be
closed
and supported by a shaft in a rotating bearing. In that case, middlings may be
introduced
into the drum through the apertures (12) along the top of the cylindrical wall
of the drum.
Alternately the second drum wall may be supported by a slewing ring attached
to said
second end wall and supported by rollers, or maybe supported by a turn table
bearing
(similar to a very heavy Lazy Suzan bearing) to provide rotatable support to
the second
wall, allowing middlings to flow into the drum through the centre of the
slewing ring or
of the table bearing through a rotary seal. In cases where middlings flow into
the drum
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through a concentric opening in the second end wall, a rotating seal mounted
concentric
with the slewing ring or turn table bearing will prevent spillage of
middlings.
Middlings enter the rotating drum and intimately mix with the rotating bed of
balls, which balls are oleophilic and strip bitumen from said middlings.
Rotation of the
drum, and its bed of tumbling and revolving balls, serves to scavenge for and
strip most
of the contained bitumen from the middlings to yield a debitumenized aqueous
phase
containing suspended solids. The resulting aqueous phase effluents of the
middlings
feedstock, after being processed by balls in this manner, can flow out of the
drum through
open apertures and through the spaces between cable wraps that cover the
cylindrical
drum wall, along the left (10) of the drum in Fig. 3. These effluents or
tailings contain
very little bitumen and may be sent to a tailings pond or may be centrifuged
to remove
solid particulates, and then reused in the process to produce more slurry for
the PSV. A
second or third modern oleophilic sieve may be used in series with the first
or second
modern oleophilic sieve in case the tailings leaving the first or second
oleophilic sieve
still contain an amount of desirable bitumen. Since sieving normally takes
less than 3
minutes per sieve, using several sieves in series does not appreciably
increase overall
processing time.
Bitumen phase captured from middlings by the revolving bed of balls
accumulates in the voids between the balls and is continuously kneaded and
then
extruded by the revolving balls through the drum apertures along the right
bottom (13)
and along the right side (11) of the drum in Fig. 3. The bitumen phase being
extruded
through the drum apertures, flows towards the cable wraps in contact with the
apertured
cylindrical drum wall, adheres to the cable wraps and often fills the spaces
between the
cable wraps for conveyance to the bitumen removal zone. The cable wraps leave
the
rotating aperture drum wall at a location (14) near the top right side of the
drum for
conveying captured bitumen phase to the bitumen removal zone where the bitumen
is
removed from the cable wraps. In Fig. 3 the bitumen removal zone is located
above the
drum and is illustrated by two adjacent rollers. These rollers also are
mounted in bearing
that support end shafts of the rollers. As shown in the Figure, bitumen on the
sieve may
be heated before entering the bitumen removal zone.
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Thus, the drum serves as the separation zone for the middlings and the rollers
shown at the top of the Figure serve as the bitumen removal zone. Bitumen on
the rising
Sieve (15) along the right side of the Figure may be heated if so desired
before reaching
the bitumen removal zone. This represents very efficient heating since the
product
volume is smaller than the feedstock (middlings) volume and the bitumen
product has a
lower specific heat than the feedstock, due to its lower water content.
Several methods of
bitumen removal have been claimed by the inventor and one very convenient
method
uses rollers with grooves on their surfaces that are large enough to allow
passage of the
cable wraps but that are small enough to squeeze most of the bitumen off the
cable wraps
for deposit as product in a receiver (16) shown below the rollers for removal
and further
processing. .
Fig 4 is an illustration of Fig. 3 imposed on a simplified Fig. 1 where a
modern
Oleophilic sieve like the one of Fig. 3 replaces the TORV and hydrocyclone of
Fig. 1 and
simplifies the flow diagram of Fig. I by eliminating several flow loops.
However mining,
moving, crushing cyclo feeding and slurry pipelining are generally unchanged;
and the
PSV has only been modified by adding a cold water (23) inlet or inlets. The
diagram is
not to scale since a PSV normally is much larger than an Oleophilic sieve.
There are two
bitumen products in this Figure, a high grade bitumen froth (20) product
coming from the
PSV and a raw bitumen (21) product from the modern Oleopilic Sieve (22). The
froth
product (20) is cleaner than conventional PSV froth since residence time in
the PSV has
been reduced, which causes only the larger and cleaner aerated bitumen
particles to have
time enough to reach the top of the PSV to be skimmed off. Cold water (23) is
introduced into the bottom of the PSV to drive mineral fines and residual
bitumen out of
the primary tailings before these leave the bottom of the PSV as will be
explained in the
description of Fig. 5. The Sieve tailings (24) may be processed separately or
may be
combined with the primary tailings (25). It is noteworthy that Primary
Tailings of Fig. 4
will be cleaner than the Bottoms of Fig.1 and Sieve Tailings (24) of Fig. 4
may be cleaner
than the TORV Tailings of Fig. 1 due to apparatus changes that may be observed
when
comparing Fig. 4 with Fig. 1. Not only is the residence time in the PSV
reduced
significantly but the apparatus is simplified by replacing with one or more
Oleophilic
sieves the TORV and hydrocyclone of Fig. 1. Alternately, modern Oleophlic
Sieves may
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replace sub-aeration bitumen froth flotation cells as discussed above. It is
noteworthy
when comparing Fig. 4 with Fig.1 that the front end, including mining, moving,
crushing,
cyclo feeding and slurry pipelining has not been changed. Alternately, when a
conditioning drum is used in the original commercial oil sand extraction
plant, instead of
a slurry pipeline, this conditioning drum is not replaced, but the slurry from
this
conditioning drum flows into the PSV of Fig. 4 without changing the front end
of the
alternate original commercial plant.
An older type of oleophilic sieve may be used as well in this case with good
results but a modern oleophilic sieve is expected to give better performance.
Water is added to the process of Fig. 4 in three locations, to the cyclo
feeder, to
the thick slurry leaving the pipeline, and flood it, and to the bottom of the
PSV. The
relative amounts of water added at these three locations may be optimized to
improve
overall bitumen recovery when oleophilic sieves are used for middlings
treatment. For
example, the amount of warm flood water (26) added to the thick slurry may be
reduced
and the amount of cold water (23) added to the PSV may be increased if that
results in
higher overall bitumen recovery or results in lower overall water demand or
energy
demand. Furthermore, the amount of NaOH or other process aid added to the
water (27)
entering the cyclo feeder may be reduced if that will improve overall bitumen
recovery or
reduce chemical demand without reducing overall bitumen recovery.
Fig. 5 is a detail drawing of Fig. 4 showing how the PSV may be integrated
with
one or more oleophilic sieves. Warm oil sand slurry (30) flows into the PSV
(31) at the
top and allows bitumen droplets attached to air bubbles to rise to the top of
the PSV and
be skimmed off as bitumen froth (32) of good quality. This occurs in the warm
zone
along the upper portions of the PSV. Cold wash water (33) is introduced into
the bottom
of the PSV to cool down the resulting middlings and to wash residual bitumen
and
mineral fines out of the primary tailings (34) before leaving through the PSV
bottom
outlet. When rakes are used to plow sand and coarse solids towards the
tailings outlet,
these rakes may also server to disperse the cold wash water (33) into the
tailings before
these tailings leave the PSV. As a result of the wash water, the resulting
tailings (34) will
contain less residual bitumen and less mineral fines than before, depending on
the amount
of cold water (33) added and therefore these tailings will dewater rapidly
either in the
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CA 02733881 2011-03-10
extraction plant or at the shore of a tailings pond, and may yield suitable
recycle process
water for immediate use by the commercial plant. Alternately, tailings (34)
and effluent
from the oleophilic sieve may be combined for shipment to a tailings pond.
Adding warm slurry at the top of a PSV and cold wash water at the bottom of
the
PSV will result in a cool zone in the bottom half of the PSV that interferes
little with the
warm zone in the top half of the PSV, because of the huge size of a
conventional PSV
especially when a target plate (36) is used to disperse warm slurry entering
the PSV while
keeping the warm slurry for a while in the upper portions of the PSV for
effective
bitumen froth flotation. The cool wash water (33) entering at the bottom,
serves to cool
the middlings to a temperature optimum for separation by an Oleophilic sieve.
It serves
to reduce the energy requirements of the commercial PSV and increases the
viscosity of
bitumen droplets in the middlings for better subsequent t recovery with an
oleophilic
sieve. Bitumen of low viscosity is not as easily recovered by an oleophilic
sieve as
bitumen of higher viscosity. This is in contrast with conventional bitumen
froth flotation,
where low viscosity bitumen is preferred. That is the reason why the PSV of
Fig. 5
preferably has a warm zone where the bitumen droplet viscosity is low for
optimum
bitumen to air attachment and resulting bitumen froth flotation, and has a
cool zone
where the bitumen droplet viscosity is higher for optimum subsequent recovery
of
bitumen with a modern oleophilic sieve. The demarcation between warm zone and
cool
zone is not at a fixed PSV level but is gradual.
From the PSV the cool middlings flow into one or more oleophilic sieves in
parallel or in series. Sieves are placed in parallel to allow an increase in
middling flow
rate. Sieves are placed in series to either to improve bitumen recovery or
also may be
placed in series to allow washing of the bitumen product with water to remove
hydrophilic minerals as described with Fig. 6.
Normally a PSV in a commercial bitumen froth flotation extraction plant
requires
a residence time of about 45 minutes to optimize bitumen froth recovery in the
PSV and
then about another 45 minutes is required for secondary bitumen recovery with
a TORV
or with sub-aeration bitumen froth flotation cells. This amount of processing
time may
be drastically reduced by using one or more oleophilic sieves to replace the
TORV or the
sub-aeration cells and by force feeding the PSV to skim off high quality
bitumen froth
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CA 02733881 2011-03-10
from the top, leaving the remaining bitumen for recovery by modern oleophilic
sieves.
Force feeding the PSV of Fig. 5 to remove rocks, gravel and coarse sand from
the slurry
and to cream off high quality bitumen froth while allowing oleophilic sieves
to capture
the remaining bitumen may halve the 45 minutes of residence time normally
required for
a conventional PSV. Using one or more oleophlic Sieves instead of a TORV with
its
attendant flow loops illustrated in Fig. 1 will in a major way reduce
processing time for
the recovery of secondary bitumen product. Therefore, for commercial mined oil
sands
plants the projected processing time of the system of Fig. 5 will be much
shorter than the
processing time of the system of Fig. 1. Reducing the required processing time
in a
commercial oil sand plant in this manner will result in major cost reductions
for bitumen
production. A further anticipated cost benefit will come from the higher
bitumen
recovery efficiency of the proposed plant modifications shown in Fig. 4 and 5,
since
recovering more bitumen from the same feedstock reduces the cost of bitumen
production. As explained below, a yet further anticipated cost benefit comes
from the
potential elimination of long duration mined oil sands tailings ponds, which
elimination
may become a possibility when oleophilic sieves are integrated into a
commercial oil
sands extraction plant and are used for processing middlings
Oleophilic sieves are not as dependent on pH as sub-aeration flotation cells.
Replacing conventional secondary bitumen recovery equipment by oleophilic
sieves has
the added advantage that the middlings from a commercial plant may be
neutralized prior
to processing. It is expected that the resulting tailings will dewater much
faster than the
current commercial fluid tailings. In the application shown in Fig. 5, an
optional reagent
(37) may be added to the middlings of Fig. 5 to reduce the pH of the
middlings, to
improve bitumen recovery by a modern Oleophlic Sieve, to encourage ultra-fine
minerals
to adhere to bitumen surfaces and/or to help reduce electrical charges that
are present on
the clay platelets of the fines in the middlings. This reagent may be carbon
dioxide, milk
of lime or some other suitable multi-valent chemical, or it may be a suitable
polymer.
Originally a process aid (27) was added to the cyclo feeder of Fig. 4 to
disperse
the oil sand slurry with water in the slurry pipeline and to produce soaps or
detergents by
sonification of bitumen components by sodium hydroxide, to disengage bitumen
from
sand, silt and clay grains of the slurry, and to encourage subsequent adhesion
of bitumen
CA 02733881 2011-03-10
to air bubbles for effective primary froth flotation in the PSV. However, for
processing
of cool middlings by modem oleophlic sieves, the pH of the middlings may be
neutralized without negative impact on middlings sieving, by the use of an
acid, such as
carbon dioxide dissolving in water or other acid, or by the use of a
multivalent
demulsifier; provided that this acid or demulsifier will not make water from a
tailings
pond unsuitable for reuse in the bitumen extraction process of the commercial
plant.
Fig. 6 is a flow diagram for water washing of bitumen product. When doing
pilot
plant test work with tailings pond sludge (fluid tailings) the present
inventor discovered
that using water to wash hydrophilic mineral particulates out of the bitumen
product from
an oleophilic sieve would yield a cleaner product. This discovery was
disclosed in
Canadian patent application 2,704,175 in which a vena contracta was used to
blend wash
water with bitumen product for clean-up. However any other method for mixing
raw
bitumen product with wash water to remove hydrophilic minerals from raw
bitumen
product may be used to achieve similar but perhaps lesser results. Not only is
this method
suitable for improving the quality of bitumen product from a modem oleophilic
sieve but
it also is suitable for improving the product quality of bitumen froth. Using
an oleophilic
sieve to process bitumen froth to clean it up has the added advantage that the
oleophilic
sieve is well suited for allowing the release of air without the need for
steam to achieve
deaeration of the froth.
Neutralizing middlings or adding emulsion breakers or multivalent chemicals to
middlings have important benefits for the resulting tailings that flow into a
tailings pond.
Conventional tailings that result from processing oil sand slurries in mined
oil sands
plants form clay card house structures in tailings ponds in which the edges of
the clay
platelets have an electrical charge that is opposite to the polarity of the
electrical charge
of the faces of the clay platelets. For clays of conventional micron sizes,
electrical
charges on clay edges of opposite polarity to the electrical charges on the
clay faces cause
the clay platelets to form card house structures. In some cases, ultra-fine
clay minerals,
when these report to the tailings ponds of conventional oil sands plants form
colloidal
gels that enclose the clay card house structures and prevent or delay in a
major way fluid
tailings dewatering once these fluid tailings have compacted to a water
content less than
65 percent. The reagent or reagents added to the middlings of Fig. 5 are
intended to serve
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CA 02733881 2011-03-10
the dual purpose of causing ultrafine mineral particles to coat bitumen
droplets of the
middlings and to reduce the opposing electrical charges on the edges versus
faces of clay
particles that result in card house structures after these middlings are
debituminzed and
become part of the tailings pond fluid tailings. The reagent (37) added to the
middlings
of Fig. 5 may also be a multivalent chemical, such as calcium hydroxide,
calcium
sulphate, calcium chloride or multivalent salts of aluminum or iron. The
reagent serves
to coat the bitumen droplets of the middlings of Fig. 5 with ultra-fines and
thus remove
altrafines from the aqueous phase of the middlings. When the middlings are
tumbled
with balls in the drum of the separation zone of the sieve, these balls will
transfer
ultrafines from the bitumen surfaces to the interior of the bitumen phase that
subsequently is extruded through the drum apertures to the cable wraps on the
outside (11
and 13) of the drum of Fig. I. The mechanism of bitumen extrusion through the
drum
wall apertures was described with Fig. 3.
Thus, not only does the reagent(37) added in Fig. 5 cause transfer of
ultrafines
from the middlings aqueous phase to the bitumen phase in the Oleophilic sieve
separation
zone, but it may also serve to a degree in discharging the opposing electrical
charges on
the clay platelets that, without such discharge, would yield a higher degree
of card house
structuring in the fluid tailings after these have reported to the tailings
pond of a
conventional mind oil sands extraction plant. Removing ultra-fines and
dissipating
opposing electrical charges on clay platelets from middlings and hence from
the resulting
fluid tailings will allow these fluid tailings to compact faster and may
eventually
eliminate mined oil sands tailings ponds. Ultra-fines are highly reactive due
to their small
size and resulting high specific surface area, and normally only form a very
small
percentage of the mass of oil sand slurries or middlings. After ultrafines
have been
transferred to the bitumen phase product of an Oleophilic sieve, these
ultrafines will, due
to their extremely small size, largely remain with the bitumen product during
water
washing and may also remain with the bitumen product during any additional
bitumen
clean up required before bitumen upgrading to synthetic crude oil, such as
dilution
centrifuging or parallel plate settling.
Thus caustic soda process aid was added to conventional mined oil sand ore to
create a slurry in which bitumen disengages from mineral grains, by means of
detergents,
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CA 02733881 2011-03-10
such as sodium naphthanates by a process similar to saponification and to
create
electrical charges on the mineral particles to disperse the slurry and thin it
so that aerated
bitumen droplets can find enough freedom to rise to the top of a PSV in the
presence of
downward settling slurry for primary recovery of bitumen by skimming it of the
top of
the PSV. It also serves as an aid in subsequent tailings oil recovery vessels
or in sub-
aeration cells to optimize secondary bitumen recovery from the middlings in
conventional commercial mined oil sand extraction plants. Caustic soda is a
beneficial
process aid to maximize bitumen recovery from oil sand slurry by froth
flotation but its
use has serious drawbacks downstream from the extraction plants after the
tailings have
entered tailings holding ponds. At the ponds, the coarse sand is removed,
either by
hydrocyclones or by conventional settling and the resulting fluid tailings
flow into
sedimentation regions of the ponds to settle and gradually compact to mature
fluid
tailings with water content approximating 65 percent. After that, the
electrical charges on
clay platelets of the fluid tailings resulting from the prior use of caustic
process aid to
form card house structures while oil sand ultrafines, reporting to the
tailings form
colloidal gels that further bind the fluid tailings and reduce the release of
water from the
fluid tailings after maturing.
The objective of the present invention is to take advantage of conventional
caustic
process aid to optimize the release of bitumen from mineral grains during
slurry
preparation and to optimize the rise of aerated bitumen droplets in a
conventional PSV to
cream off a high grade primary bitumen froth from the top of said PSV at a
temperature
optimum for bitumen froth flotation. A further objective of the present
invention is to
add cold wash water to the bottom of the PSV to wash fines and residual
bitumen out of
the primary tailings leaving the PSV at its bottom outlet and to add these
fines and
residual bitumen to the middlings that leave from the middle of the PSV. It is
a further
objective of the present invention to create a warm zone with temperature
optimized for
bitumen froth flotation along the top of the PSV to cream off a high grade
bitumen froth
and to create a cool zone lower down in the PSV with temperatures optimized
for
subsequent processing of middlings by one or more oleophilic sieves. It is yet
a further
objective of the present invention to add a reagent to the middlings going to
the
oleophlilic sieve(s), which reagent serves to cause altrafines to adhere to
bitumen
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CA 02733881 2011-03-10
surfaces and to cause clay particles to lose at least part of their electrical
charges before
leaving the oleophilic sieves as tailings effluent. A yet further objective of
the present
invention is to transfer ultrafine particles from bitumen surfaces to the
interior of bitumen
products of oleophilic separation of said middlings. Another objective of the
present
invention is to yield tailings that will settle and compact faster than
conventional oil sand
tailings, either naturally in a pond, or by means of centifuges or
hydrocyclones.
As illustrated in Fig. 6, raw bitumen (40) from a modem oleophilic sieve or
bitumen froth (41) from a PSV or from secondary bitumen froth flotation may be
washed
with water (42) to remove hydrophilic mineral particulates. This is
accomplished by
thoroughly mixing the bitumen product (40) and/or the bitumen froth (41) with
water
(42) in a mixer (43), and then separating the resulting mixture by means of an
oleophilic
sieve (44). Cleaner bitumen is recovered at the bitumen removal zone (45) of
the sieve,
and the effluent (46) consisting of water containing hydrophilic minerals
leaves the
modem oleophilic sieve for temporary disposal or for centrifuging to reuse the
resulting
water cut in the commercial process. As noted before, air entrained in the
original froth
processed by an oleophilic sieve in this manner can readily escape through the
open
apertures along the top of the drum (47)
Thus far in the description of the present invention, it is proposed that the
existing
commercial mined oil sands plants will be modified to allow middlings to be
optimized
for secondary bitumen recovery by one or more oleophilic sieves. However
industry may
not be willing initially to invest in such plant changes due to the high cost
of shutting
down an existing commercial oil sands plant which shut down may be needed for
such
modifications. For that reason, an alternate objective of the present
invention is to
process commercial oil sand tailings after these arrive at the tailings ponds
to convince
the oil sands industry of the merits of modern oleophilic sieve processing of
live oil sand
streams.
Current objectives of commercial processing of mined oil sands is to deposit
the
tailings of primary and secondary bitumen extraction into tailings ponds for
several years
of settling and compacting into mature fluid tailings. Then the mature fluid
tailings are to
be pumped or dredged out of the bottom of tailings ponds to process these to
optionally
remove the residual bitumen and add polymers or gypsum to the fluid tailings,
or to the
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CA 02733881 2011-03-10
debitumenized fluid tailings, and mix these with dry sand to form a remediated
landscape
after a portion of an oil sands lease has been mined out. As a result of the
maturing
process, microbial action will consume some of the residual bitumen found in
fluid
tailings and convert it to methane that is released to the atmosphere.
Maturing of the
fluid tailings causes oxidation of the contained bitumen, which results in an
increase in its
total acid number (TAN). Bitumen characterized by high TAN, and its resulting
refinery
products will tend to play havoc with refinery equipment and therefore will
require
special treatment.
The flow diagram of Fig. 5 has illustrated the use an oleophilic sieve to
process
middlings. However, fluid tailings of a tailings pond, after rocks, gravel,
and sand have
been removed are very similar to middlings except that fluid tailings contain
a lower
bitumen content than middlings. Since down time at mined oil sands plants is
very
expensive, it may take some time to implement the herein proposed equipment
changes to
replace all secondary bitumen recovery equipment with oleophilc Sieves.
However to
process fresh fluid tailings will not require any changes in the existing
commercial
extraction plants but only at the tailings ponds.
The flow diagram of Fig. 7 illustrates the use of an oleophilic sieve for
processing
mined oil sand extraction tailings after these arrive at a tailings pond.
Large rocks cannot
be processed by an oleophilic sieve and gravel will blind an oleophlic Sieve.
Rocks and
20' gravel must be removed from the tailings by means of for example a grizzly
as illustrated
in Fig. 7, or by some other means. A confined path hydrocyclone disclosed and
claimed
in Canadian patent application 2,661,579 may be used subsequently to remove
gravel and
sand from the undersize stream (50) of the grizzly. This hydrocyclone allows
for the
injection of a fluid (51), such as gas, water, gas dissolved in water, or
chemical
dissolved in water into the confined path where centrifugal force drives the
gravel and
sand to the underflow and drives residual bitumen into the hydrocyclone
overflow for
processing by the oleophilic sieve. The hydrocyclone may be operated such that
the
underflow (52) is like a rope of sand and water or it may produce a flowable
slurry of
sand and water. The overflow (53), containing most of the residual bitumen of
the
original oil sand tailings (54) along with fines and ultrafines suspended in
water is very
CA 02733881 2011-03-10
similar to the middlings described in the preceeding disclosures above, except
that it will
have a lower percentage bitumen content.
Identical methods of Oleophilic sieve separation may be used for processing
confined path hydrocyclone overflow (53) of Fig. 7 as for processing middlings
of Fig. 5.
Such processing of middlings is described in the disclosure above. The bitumen
product
(55) of Fig. 7 may be processed like the bitumen product of Fig.5 and the
debitumenized
fluid tailings (56) of Fig. 7 may be processed like the effluent of Fig. 5 or
may be allowed
to settle and compact in the sedimentation zones of the tailings pond. A
reagent was
added to the middlings of Fig. 5, and a similar reagent(5 1) may be added by
injecting it
into the grizzly undersize stream (50) while flowing through the confined path
of the
hydrocyclone of Fig. 7. Of course care must be taken when injecting such
reagents to
make sure that such additions will not be detrimental to the operation of the
commercial
extraction plant. For example, injecting large amount of gypsum into the
grizzly
undersize flow (50) of Fig. 7 or into the middlings of Fig. 5 will result in
fluid tailings
that have permanent hardness due to the calcium sulphate content of the
effluent entering
the tailings ponds. As this effluent settles and compacts, the water released
from this
effluent will also have a high degree of permanent hardness, making it
unsuitable for
recycle to the commercial oil sands extraction plant unless processed to
overcome this
hardness. Injecting carbon dioxide reagent or compressed carbon dioxide
dissolved in
water into the middlings of Fig. 5 or into the grizzly undersize of Fig. 7
will tend to
reduce the pH of these streams by reacting with sodium hydroxide process aid
and
sodium based detergents. For some oil sand ores this reaction may encourage
ultrafines
to adhere to bitumen surfaces for reporting to the bitumen product and is
expected to
reduce the formation of gels in the resulting fluid tailings for faster
dewatering. Since
dewatering is a long duration process, these expectations will have to be
verified by long
duration sedimentation experiments. The main advantage of the process
illustrated in
Fig. 7 is the timely production of bitumen from tailings arriving at a
tailings pond before
this bitumen has had an opportunity to become oxidized to bitumen that has a
high TAN
(total acid number). Low TAN bitumen is preferred over high TAN bitumen for
upgrading to oil refinery products.
21
CA 02733881 2011-03-10
Therefore, as outlined above, the instant invention can function to process
middlings from a conventional commercial mined oil sands plant to improve
bitumen
recovery and product quality and especially to reduce overall processing time
of oil sand
slurry to less than half the time currently required in a commercial oil sands
extraction
plant. This may be accomplished by replacing conventional secondary bitumen
recovery
equipment with oleophilic sieves and by making minor modifications to force
feed a
conventional PSV and cream off the top a reduced amount of primary bitumen
product,
but of high quality, while allowing oleophilic sieves to recover more
secondary bitumen.
Since modifications to a conventional mined oil sands plant are expensive and
may take
some time to become acceptable, the further objective of the instant invention
is to
process conventional commercial oil sand tailings immediately or soon after
these arrive
at a tailings pond for the recovery of fresh residual bitumen before this
residual bitumen
has oxidized to become high in total acid number.
SUMMARY
The present invention may be summarized as follows
1. A method for recovering oil sand bitumen from the middlings of a mined oil
sand primary separation vessel, comprising: mining an oil sand ore from an oil
sand deposit, transporting the mined oil sand ore to an oil sand slurry
production facility, producing an oil sand slurry with the aid of water heated
above ambient temperature, air and process aid as required to yield an
aqueous slurry in which oil sand bitumen is disengaged from oil sand mineral
grains, diluting the oil sand slurry with water as required to form a diluted
slurry suitable for separating the diluted slurry in a primary separation
vessel,
introducing the diluted slurry into a primary separation vessel, skimming an
aerated primary bitumen product from the top of the primary separation vessel
for further processing, removing a primary tailings stream from the bottom of
the primary separation vessel for disposal or further processing, removing a
middlings stream from the approximate mid elevation of the primary
separaration vessel and recovering secondary bitumen product from the
middlings stream by means of one or more oleophilic sieves to yield
22
CA 02733881 2011-03-10
secondary bitumen product for further processing and yielding debitumenized
middlings for disposal or further processing.
2. A method as in Item1 wherein the oil sand ore is mined from a mine face by
means of a mechanical shovel and is transported by one or more mined oil
sand haulers to the slurry production facility.
3. A method as in Item 1 wherein the oil sand ore is hydraulically mined and
the
slurry production facility is part of a hydraulic mining facility.
4. A method as in Item 1 wherein mining of the oil sand ore is carried out
underground.
5. A method as in Item I wherein cold water is introduced into the primary
separation vessel near the bottom of the primary separation vessel to wash
residual bitumen and ultrafines out of the primary tailings stream leaving the
primary vessel to thereby dilute and cool down the middlings stream.
6. A method as in Item 1 wherein the one or more oleophilic sieve are modern
oleophilic sieves.
7. A method as in Item I wherein the secondary bitumen product is mixed with
water and one or more reagents to form an aqueous mixture in which
hydrophilic mineral particles disengage from the secondary bitumen product
and the mixture is subsequently processed by one or more oleophilic sieves to
yield a bitumen product that has a lower minerals content than the secondary
bitumen product.
8. A method as in item 7 wherein at least one of the one or more reagents is a
reagent that is known to increase the hydrophilic nature of minerals surfaces.
9. A method as in Item 1 wherein the primary bitumen product is mixed with
water and one or more reagents to form an aqueous mixture in which
hydrophilic mineral particles and air disengage from the primary bitumen
product and the mixture is subsequently processed by one or more oleophilic
sieves to yield a bitumen product that has a lower minerals content and a
lower air content than the primary bitumen product.
10. A method as in Item 1 wherein cold water introduced into the bottom of the
primary separation vessel and warm slurry introduced into the top of the
23
CA 02733881 2011-03-10
primary separation vessel results in a warm zone near the top of the primary
separation vessel optimized for bitumen froth flotation of primary bitumen
froth product in the upper portion of the primary separation vessel and
results
in cooled down middlings optimized for subsequent secondary bitumen
production from the middlings stream by means of one or more oleophilic
sieves.
11. A method as in Item 1 wherein the middlings stream is reacted with carbon
dioxide, with an acid, with a multivalent salt or with a multivalent caustic
to
encourage ultrafines to adhere to the surface of bitumen particles and/.or to
cause at least to a degree the discharge of electrical charges on clay
platelets
of the middlings before the middlings stream is processed by means of one or
more oleophilic sieves.
12. A method for recovering oil sand bitumen from the primary and secondary
tailings of a mined oil sand primary separation vessel, comprising: mining an
oil sand ore from an oil sand deposit, transporting the mined oil sand ore to
an
oil sand slurry production facility, producing an aerated oil sand slurry with
the aid of water heated above ambient temperature, air and process aid as
required to yield an aqueous slurry in which oil sand bitumen is disengaged
from oil sand mineral grains, diluting the oil sand slurry with water as
required to form a diluted slurry suitable for separating the diluted slurry
in a
primary separation vessel, introducing the diluted slurry into a primary
separation vessel, skimming an aerated primary bitumen product from the top
of the primary separation vessel for further processing, removing a primary
tailings stream from the bottom of the primary separation vessel for disposal
or further processing, removing a middlings stream from the approximate mid
elevation of the primary separaration vessel and recovering secondary
bitumen product from the middlings stream to yield a secondary tailings
stream that is combined with the primary tailings stream to form a combined
tailings stream that is conveyed by pipeline to a tailings pond where rocks,
gravel and coarse sand are removed from the combined tailings stream near
the shore of the tailings pond after which the combined tailings steam is
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CA 02733881 2011-03-10
processed by one or more oleophilic sieves to recover residual bitumen
product.
13. A method as in Item 12 wherein the oil sand ore is mined from a mine face
by
means of a mechanical shovel and is transported by one or more mined oil
sand haulers to the slurry production facility.
14. A method as in Item 12 wherein the oil sand ore is hydraulically mined and
the slurry production facility is part of a hydraulic mining facility.
15. A method as in Item 12 wherein mining of the oil sand ore is carried out
underground.
16. A method as in Item 12 wherein the one or more oleophilic sieve are modern
oleophilic sieves.
17. A method as in Item 12 wherein the secondary bitumen product is mixed with
water and one or more reagents to form an aqueous mixture in which
hydrophilic mineral particles disengage from the secondary bitumen product
and the mixture is subsequently processed by one or more oleophilic sieves to
yield a bitumen product that has a lower minerals content than the secondary
bitumen product
18. A method as in item 17 wherein one of the one or more reagents is a
reagent
that is known to increase the hydrophilic nature of minerals surfaces.
19. A method as in Item 12 wherein the primary bitumen product is mixed with
water and one or more reagents to form an aqueous mixture in which
hydrophilic mineral particles and air disengage from the primary bitumen
product and the mixture is subsequently processed by one or more oleophilic
sieves to yield a bitumen product that has a lower minerals content and a
lower air content than the primary bitumen product.
20. A method as in Item 12 wherein the middlings stream is reacted with carbon
dioxide, with an acid, with a multivalent salt or with a multivalent caustic
to
encourage ultrafines to adhere to the surface of bitumen particles and/or to
cause at least to a degree the discharge of electrical charges on clay
platelets
in the middlings stream before the middlings stream is processed by means of
one or more oleophilic sieves.
