Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Jan Kruyer, P.Eng. Thorsby, AB.
SPEED OF SEPARATION - MINE FACE OIL SAND
EXTRACTION.
RELATED APPLICATIONS
This application is related to Canadian Patent Application number 2,661,579
filed April 9th, 2009 entitled " Helical Conduit Hydrocyclone Methods, number
2,638,551 filed August 7th , 2008 entitled "Sinusoidal Mixing and Shearing
Apparatus and Associated Methods ", number 2,638,596 filed August 6tt', 2008
entitled "Endless Cable System and Associated Methods ", number 2,666,025
filed
May 19th, 2009 entitled "Pond Sludge Bitumen and Ultra Fines Agglomeration and
Recovery ",and number 2,690,951 filed January 27th, 2010 entitled `Endless
Cable
BeltfllignmentApparatus and Methodsfor Separations".
RELATED PATENTS
Reference is also made to Canadian patent 918,588 entitled "Hot Water
Process Conditioning Drum " granted to Marshall et. al. on January 9th, 1973,
to
Canadian patent 1,141,318 entitled "Conditioning Drum for Slurries and
Emulsions"
granted to the present inventor on February 15th, 1983, to Canadian patent
2,029,795
entitled "Pipeline Conditioning Process for Mined Oil-Sand" granted to George
J.
Cymerman November 5th, 1996, and to 1,232,854 entitled "Use of a Submersible
viscometer .... Hot Water Process... " granted to Laurier L. Schramm April
16th, 1988
FIELD OF THE INVENTION
The present invention relates to methods for rapidly separating oil sand ore,
potentially close to an oil sand mine face, using an apertured oleophilic
screen to
capture bitumen from oil sand slurry on surfaces of the screen but to allow de-
bituminized aqueous phase of the slurry to pass to disposal through apertures
of the
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Jan Kruyer, P.Eng. Thorsby, AB.
screen. Accordingly, the present invention involves the fields of process
engineering,
chemistry, physical chemistry and chemical engineering.
BACKGROUND OF THE INVENTION
In the present invention a revolving apertured oleophilic screen, preferably
in
the form of closely spaced endless cable wraps is used to separate an oil sand
slurry
produced from crushed oil sand ore mixed with water. A number of Canadian
patents
pending for the present inventor describe in detail the construction of and
methods for
the use of apertured oleophilic screens to achieve separations. In separation
zones
bitumen is captured by the screen surfaces whilst de-bituminized slurry or
mixture
passes to disposal through the screen apertures. In bitumen recovery zones,
bitumen,
is stripped from the screen surfacess by various methods, such as for example,
are
described in granted and copending Canadian patent applications, some of which
also
are pending in the U.S. or have been granted there. Many types of separation
zones
and many types of bitumen removal zones have been described by the inventor in
the
above referenced patent applications. The present invention makes use of the
fact
that separating oil sand slurry by means of an oleophilic apertured screen is
about ten
times as fast as separating oil sand slurry by the conventional method of
bitumen
froth flotation. When a process is ten times as fast, the equipment needed to
achieve
that separation can be much smaller and more economically viable. It opens the
possibility of moving the separation equipment as the oil sand mine face
recedes, and
the mining and ore transporting equipment follows the receding mine face.
The specifications of the above referenced prior patents and of the presently
pending applications provide extensive details as to the size and composition
of the
Alberta oil sands resource. Those specifications also describe various methods
used
for separations that use revolving oleophilic apertured screens and provide
details on
the chemistry of oil sands separation. For that reason, reference is made
hereby to
disclosures detailed in these referenced patents and applications. For the
sake of
brevity, these details are not repeated here, except when these apply
specifically to
the present invention.
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Jan Kruyer, P.Eng. Thorsby, AB.
HIGH SPEED CATERACTING DRUMS
The present invention discloses a unique method of using a high speed
rotating cateracting drum to rapidly produce a dilute slurry of crushed mined
oil sand
and water that is suitable for separation by a revolving apertured oleophilic
screen
after oversize material has been removed from the slurry by grizzly and/or
hydrocyclone. The drum is operated in cateracting mode and does require the
use of
steam sparging to prepare a slurry for separation. As a potentially alternate
method of
slurry preparation the present invention makes use of highly turbulent flow in
a
serpentine pipe described in Canadian patent application 2,638,551. Again,
oversize
is removed from the slurry by means of a hydrocyclone before separation. One
hydrocyclone specifically designed for that purpose is disclosed in Canadian
patent
application 2,661,579.
Current commercial oil sand separation plants use two methods for preparing
oil sand slurries. In the most recently built commercial plants, the oil sand
ore is
crushed by means of roller crushers and then is mixed with hot or warm water
containing a process aid such as, for example, sodium hydroxide. This mixture
is
pumped through a generally straight pipeline in turbulent flow, in the
presence of air
and process aid, to disengage oil sand bitumen from sand grains of the oil
sand ore
and to form a thick aerated slurry that is suitable for separation by bitumen
froth
flotation after it is flooded with dilution water. Such a pipeline slurry,
before flood
water is added, may contain by weight 70.4% solids, 20.5% water and 9.1%
bitumen.
Its water content is kept low on purpose to encourage the entrainment of air
in the
slurry before flood water is added. After the flood water is added, the
released and
dispersed air bubbles are free to help bitumen rise to the top of separation
vessels by
froth flotation in the thin slurry. Air is supplied at the entrance of the
slurry pipeline
and may also be added to the thick slurry as it flows through the pipeline.
After flood
water is added, the slurry flows into separation vessels where aerated bitumen
rises to
the top and is skimmed off. The composition by weight of flooded slurry may
then
be 50% solids, 43% water and 7% bitumen. The above and below information about
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Jan Kruyer, P.Eng. Thorsby, AB.
conventional oil sands plants is readily obtainable from a review of the prior
art found
in published literature and in patents open to the public.
In contrast to oil sand slurry production by means of a pipeline, commercial
oil sands plants that were build some years ago, make use of slowly rating
conditioning drums in which the oil sand and water mixture tumbles in the drum
in
gently mixing or cascading mode to produce a thick oil sand slurry that may
contain
by weight 68.3% solids, 22.8% water and 8.9% bitumen. Steam enters such a drum
through sparging valves feeding perforated steam ducts mounted along the
internal
periphery of those drums, sparge steam into the slurry. The composition of the
slurry
produced in these drums is very similar to that of the thick slurry produced
by an oil
sand slurry pipeline. Of coarse, commercial oil sand slurry will vary with the
type or
composition of the oil sand ore being processed.
A commercial conditioning drum typically is 5.5 meters in diameter, 30.5
meters long and revolves at about 3 RPM. The critical speed of a drum of that
size is
18 RPM, indicating that these commercial conditioning drums rotate at about
17% of
their critical speed. This drum rotation speed results in cascading of the
contents
inside the drum, but does not normally provide for cateracting of the oil sand
drum
contents. These drums are not designed to operate in cateracting mode. Gentle
mixing of oil sand ore with water and air to conditioning it and form a thick
slurry at
elevated temperature for subsequent separation by bitumen froth flotation is
the
objective of these conditioning drums.
For current commercial oil sands plants, process water used for producing oil
sand slurry must be low in dispersed solid content to achieve acceptable
bitumen
recovery since fines tend to interfere with the efficiency of froth flotation.
This
applies to water used to produce un-flooded oil sand slurry and also applies
to the
dilution water used to flood the slurry before separation. That is the reason
why
recycle water used for the current commercial plants is taken from the very
top of its
tailings ponds where most of the solids have settled for years to lower levels
in the
ponds.
The present invention discloses a method for producing a slurry that is
suitable for separation by a revolving oleophilic apertured screen. For
effective
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Jan Kruyer, P.Eng. Thorsby, AB.
separation, this screen requires a slurry that is thinner than the thick
aerated slurry
currently produced commercially by pipeline or by a slowly turning
conventional
conditioning drum, but that may be thicker than the conventional thin slurry,
flooded
by water to make it suitable for separation by bitumen froth flotation. The
desired
slurry for oleophilic screen separation does not contain any significant
amounts of air
and may be produced by means of a serpentine pipe disclosed in patent
application
2,638,596 or may be produced by a rapidly turning slurry drum operating in
cateracting mode as disclosed in the present invention. This slurry drum is
provided
with crushed oil sand at ambient temperature and warm or hot water is added to
produce a slurry with an average temperature, somewhere between 20 and 50
degrees
centigrade depending on oil sand composition and apparatus configuration. The
required temperature of the added water is a function of the season and of the
temperature and frozen or unfrozen nature of the mined oil sand ore. Unlike
conventional oil sand conditioning drums, the cateracting slurry preparation
drum of
the present invention does not have any provision for injecting steam into the
drum or
into the slurry but, in addition to turning faster, may be provided with
longetudinal
lifters mounted along the drum interior cylindrical wall to encourage
cateracting of its
contents at drum rotational speeds higher than conventional conditioning
drums. The
produced slurry contains by weight between 65% and 55% solids and between 25%
and 40% water, and the drum rotates at between 30% and 80% of its critical
speed
(i.e. RPM). The cateracting contents of the drum creates a high degree of
turbulence
in the drum interior, causing rapid conversion of mined oil sand and water
into an oil
sand slurry. Cateracting drum rotating at those speeds can producing an un-
aerated
dilute slurry much faster than current commercial slurry tumbling drums that
turn at
about 17% of critical speed and produce a thick aerated slurry. The current
commercial drums require a residence time of about 3 or 4 minutes. The drum of
the
present invention can be much smaller for producing the same amount of slurry
per
hour and requires a residence time for slurry production of less than 2
minutes and
less than lminute in some cases. Hardened teeth may be mounted inside the drum
to
break up cascading lumps of oil sand ore to speed up the ablation process. In
the
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Jan Kruyer, P.Eng. Thorsby, AB.
present invention, neither steam nor air are needed in the drum to produce a
slurry for
subsequent separation by a revolving apertured oleophilic screen.
A unique feature of the present invention is that the equipment required to
separate an oil sand slurry by sieving is about one tenth to one twentieth the
required
size of conventional equipment for separating an oil sand slurry by froth
flotation.
The resulting size reduction in required equipment, both for slurry production
and for
slurry separation may make it possible to move the complete separation plant
continuously with the receding mine face, or from time to time as required,
and thus
keep it in close proximity to the mining equipment that moves with the mine
face.
Such a dramatic and unexpected change in plant size and configuration will
have a
major and beneficial impact on the cost of future mined oil sands plants; both
in
capital cost and also in operating cost, including the cost of materials
handling.
Thus, to summarize slurry production, the present invention produces a slurry
from mined oil sand; a slurry that generally has a composition of intermediate
solids
content as compared with the slurries currently prepared for commercial oil
sand
separation. It contains between 65% and 50% solids by weight. The slurry has a
solids content and a water content that is between the conventional thick
aerated
slurry and the conventional flooded slurry of the current commercial oil sands
plants.
To produce thick aerated slurry, the conventional commercial plants use a
pipeline to
mix the ore with water and air in turbulent flow or use very large
conditioning drums,
rotating in cascading mode, with a length to diameter ratio of greater than 5
at a rate
of rotation less than 18% of critical speed and gently mix the ore with water
and air,
and/or with steam that is sparged into the drum contents to produce thick warm
aerated slurry. The thick aerated slurry of the current commercial plants,
containing
about 68% solids, is flooded with water, to reduce its solids content to about
50%
before it enters the froth flotation separation vessels. In contrast, an
object of the
present invention is that the slurry must cateract inside the slurry
preparation drum for
fast ablation. It does not flow to a froth flotation vessel but may pass
trough a grizzly
and/or hydrocyclone to remove oversize material that may hinder the effective
separation of this slurry of interemediate composition by a revolving
apertured
oleophilic screen or may abrade the screen. Before separation, it is first
agglomerated
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Jan Kruyer, P.Eng. Thorsby, AB.
to increase bitumen particle size after which it flows to an apertured
oleophilic screen
for separation.
Sparging steam is not used in the present invention but warm or hot water are
used to produce a slurry, year round, that has a temperature below 50
centigrade.
Since air entrainment in the slurry is not desired, the slurry can be made
rapidly in
drums that rotate at high RPM, in excess of 30% of the critical drum speed,
and
preferably at higher rotational speeds unless excessive stresses on the drum
structure:
limit the drum speed. Hardened teeth may be mounted inside the drum to help
break
up cascading large oil sand lumps. Rocks and gravel of the oil sand ore
cascading in
the drum also serve to break up oil sand lumps. Since the temperature of the
produced
slurry of the present invention can be lower than the temperature of
conventional
slurry of the prior art, steam is not required in the slurry preparation drum
of the
present invention.
Since, unlike froth flotation, separation of oil sand slurry by an apertured
oleophilic screen is very tolerant of the fines in the process water, tailings
run off
water may be recycled while still warm. That means, water used for making
slurry in
the present invention may use hot water in combination with oil sand tailings
pond
water or with warm or lukewarm tailings run off water.
In addition to deviating from the conventional practice of mined oil sand
slurry production, the present invention also reduces in a major way the size
of the
separating equipment by using bitumen agglomeration and screening that is
generally
an order of magnitude faster than froth flotation. For flotation the aerated
bitumen
has to struggle in its upward movement against settling sand and fines in
aqueous
suspension in tall and large diameter separation vessels. The rising bitumen
takes a
long time to rise to the top of the separation vessels. However, the cost of
commercial froth flotation equipment does not allow major extensions of the
extraction plant residence time. That is the reason why bitumen mats float on
top of
the current tailings ponds, since in the ponds the very fine bitumen particles
have
adequate time to rise to the top. Unfortunately, these floating bitumen mats
have
resulted in the death of may birds landing on these mats. This currently this
is the
topic of a major court case
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Jan Kruyer, P.Eng. Thorsby, AB.
For oleophilic sieving, the slurry passes through a revolving apertured
oleophilic screen to separate the contained bitumen from the aqueous phase of
the
slurry. Prior bitumen agglomeration serves to increase bitumen particle size
to
increase the effectiveness of bitumen capture by the oleophilic screen
surfaces. Pilot
plant test have shown that screening bitumen can capture more bitumen from oil
sand
slurry than froth flotation, and do it faster. Faster processing allows a
reduction in the
required size of commercial equipment and this is bound to make oil sand
separation
less expensive. Small equipment also is easier and cheaper to move than large
equipment.
Smaller equipment size does not necessarily mean a reduction in the diameter
of the slurry preparation drums but mostly means a reduction in the length of
the
drum. Thus, for example a 5 meter diameter 30 meter long drum may be reduced
to a
5 meter diameter, 5 meter long drum to achieve a reduction in equipment size
of a
factor of 6.
However reducing the drum diameter from 5.5 meter to 2.2 meter, while keeping
it 30
meters long to achieve the same reduction in equipment size normally is not an
option. Reducing drum cross sectional area for speeding up slurry production
is less
effective than reducing the drum length. For that reason cateracting drums of
the
present invention preferably are larger than 3 meters in diameter and more
preferably
larger than 5 meters in diameter, but are much shorter than 30.5 meters. The
turbulence created in the drum by cateracting is much greater for large-
diameter
drums than for small diameter drums, since the cateracting charge falls
through a
greater distance when the drum diameter is larger, adds more energy to the
slurry and
breaks it up faster.
Cateracting drums of the present invention generally are horizontally mounted
but may be mounted at a decline that is less than 5 degrees between entrance
and exit
to improve flow of slurry to the exit. In that case, proper support of and
alignment
with slewing rings is required to keep the drum properly and efficiently
supported to
reduce wear of the slewing rings and rotating ring supports. Instead of
slewing rings
and rollers, inflated rubber tires may be used to support the drum, provided
that the
drum circumference is not deformed by the weight of the drum and its contents.
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Jan Kruyer, P.Eng. Thorsby, AB.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a flow diagram of a current commercial oil sand separation process
using bitumen froth flotation.
Figure 2 is a flow diagram of a proposed oil sands separation process that
uses
a serpentine pipe to produce an oil sand slurry and an apertured oleophilic
screen
(oleophilic sieve) to separate the slurry. It may be located close to a mine
face and by
that location may eliminate the long pipeline of Figure 1. An optional
tailings
dewatering conveyor is included in the Figure
Figure 3 is a flow diagram of a proposed oil sands separation process that
uses
a cascading slurry preparation drum. It is very similar to the flow diagram of
Figure
2 but replaces the serpentine pipe with a cascading conditioning drum and the
dewatering conveyor with optional stationary tailings dewatering.
Figure 4a is an isometric drawing of a cateracting drum of the present
invention for producing an oil sand slurry.
Figure 4b is inside view of the drum of Figure 4a through section A-A of
Figure 4a
DEFINITIONS
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 the terminology employed herein is used for the
purpose of describing particular embodiments only and is not intended to be
limiting.
It must be noted that, as used in this specification and the appended claims
the
singular forms "a", "an" and "the" include plural referents unless the context
clearly
dictates otherwise.
In describing and claiming the present invention, the following terminology
will be used in accordance with the definitions set forth below. When
reference is
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Jan Kruyer, P.Eng. Thorsby, AB.
made to a given terminology in several definitions, these references should be
considered to augment or support each other or shed additional light.
"ablation" refers to the disengaging of bitumen from sand grains of oil sand
ore in the presence of warm water. It normally occurs in a revolving drum or
in a
pipeline in turbulent flow and results in the production of oil sand slurry.
Conditioning is another term for ablation but conditioning normally includes
the use
of a process aid, such as sodium hydroxide, to disperse clay fractions of the
oil sand
ore and to react with naphthenic acids of the oil sand ore to form detergents.
Ablation
does not necessarily involve sodium hydroxide or process aid additions to
produce a
slurry.
"agglomeration" refers to increasing the size of bitumen particles in an
aqueous mixture prior to the removal of enlarged bitumen particles from the
mixture
by an oleophilic apertured wall or screen . Agglomeration may be accomplished
in a
revolving drum that contains oleophilic surfaces. For example, the apertured
walls of
the agglomerator of Figures 2 and 3 may be oleophilic, or oleophilic baffles
or
oleophilic tower packings inside the agglomerator may provide surfaces for
capturing
dispersed bitumen phase from a slurry to increase the size of the bitumen
particles by
mutual adhesion, before these are sloughed off in the form of bitumen of
increased
particle size due to drum rotation, and flow to the revolving apertured
oleophilic
screen surrounding the apertured drum wall of the agglomerator. Alternately
the
agglomerator may contain a bed of tumbling oleophilic balls that capture
dispersed
bitumen particles from the slurry and release enlarged bitumen phase particles
thereafter. During pilot plant studies, it was noted with agglomerating drums,
such as
shown in Figures 2 and 3 rotating in counter clockwise direction, that most of
the
bitumen phase flowed to the surrounding apertured oleophic screen or belt
through
the right bottom quadrant of the cylindrical drum, while most of the de-
butuminized
aqueous phase flowed to the surounding apertured belt through the left bottom
quadrant of the drum. Copending patent applications of the present inventor
provide
additional details for the construction and operation of bitumen aglomerators
that
support an apertured belt. Another alternate method, that I have used, to
provide for a
lesser degree of bitumen agglomeration makes use of rotating blades in a
vessel filled
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Jan Kruyer, P.Eng. Thorsby, AB.
with slurry. In that case, bitumen particles of the slurry, revolving in the
stationary
vessel, come in contact with other bitumen particles of the slurry and adhere
to each
other to form enlarged bitumen phase particles floating in the slurry.
"apertured agglomeration drum" refers to a rotatable drum that contains
oleophilic surfaces inside the drum and is provided with an apertured
cylindrical wall
that allows agglomerated mixture to flow to the partly surrounding oleophilic
screen
to capture bitumen. An agglomerator drum is used to increase the particle size
of
bitumen particles in oil sand mixtures prior to separation. The drum may
contain
interior oleophilic baffles or a bed of tumbling oleophilic balls. An
agglomeration
drum does not operate in cateracting mode, but rather in cascading mode well
below
30% of critical drum speed.
"bitumen" refers to a viscous hydrocarbon that contains maltenes and
asphaltenes and is found originally in oil sand ore interstitially between
sand grains.
Maltenes generally represent the liquid portion of bitumen in which
asphaltenes of
extremely small size are thought to be dissolved or dispersed. Asphaltenes
contain
the bulk of the metals found in bitumen and probably give bitumen its high
viscosity.
"bitumen phase" normally refers to small bitumen droplets that have been
agglomerated into enlarged bitumen drops or streamers. Bitumen streamers are
enlarged bitumen masses that can flow as distinct units in the presence of
aqueous
phase. Another example of bitumen streamers are the bitumen mats found at
various
levels in oil sand tailings ponds or the bitumen mats that often are found to
float on
the surface of oil sand tailings ponds. However these bitumen mats are much
larger
than the bitumen streamers that flow from an agglomerator interior to an
apertured
oleophilic screen.
"bitumen recovery" or "bitumen recovery yield" refers to the percentage of
bitumen removed from an original mixture or composition. Therefore, in a
simplified
example, a 100 kg mixture containing 45 kg of water and 40 kg of bitumen where
38
kg of bitumen out of the 40 kg is removed, the bitumen recovery or recovery
yield
would be a 95%.
"cable wraps" refers to multiple wraps of endless rope or cable wrapped
around two or more rollers or drums where the spaces between sequential cable
wraps
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Jan Kruyer, P.Eng. Thorsby, AB.
form apertures through which aqueous phase can pass, giving up some or most of
its
bitumen content to the wraps as bitumen phase passes by and contacts the
wraps.
Alternately it refers to adjacent single endless ropes or cables in contact
with
supporting rollers or drums. An endless cable may have multiple wraps or
multiple
single endless cables may be placed next to each other to form a sieve whereby
aqueous mixture can pass between the cable wraps and bitumen may be captured
by
the wraps.
"cateracting slurry" refers an oil sand slurry inside a slurry preparation
drum
that rotates fast enough that some of the slurry containing lumps of oil sand,
rocks
and gravel are lifted away from the main slurry bed in the drum and fall back
down
into the slurry bed. When a slurry drum rotates at about 20 percent of
critical speed,
the slurry bed represents a tumbling bed in which the slurry tumbles inside
the bottom
portion of the drum. Current commercial oil sand conditioning drums operate
with a
gentle tumbling bed to form oil sand slurry and normally do not turn faster
than 25%
of the critical drum speed. In a cateracting slurry drum the solids and slurry
continuously dropping in free fall from above onto and into the slurry bed of
the drum
create a zone of very high turbulence that serves to very quickly convert a
mixture of
oil sand and water into a slurry suitable for separation by an apertured
oleophilic
screen. Cateracting normally takes place when the critical speed of the drum
exceeds
70% of critical speed. However longitudinal flights mounted along the interior
of a
slurry drum, that serve as lifters of the undigested oil sand ore can induce
cateracting
in the drum at significantly lower drum speeds, down to 30% of the critical
drum
speed
"critical speed" of an agglomerator drum is the speed of rotation of an
agglomerator drum, containing a bed, in which at least 5% of the bed inside
the drum
remain in contact with the drum wall at all times due to centripetal force and
due to
adhesion to the drum wall by bitumen at process temperature. For a conical
agglomerator drum, critical speed computation of the drum is based on the
largest
internal diameter of the conical drum. In an agglomeration drum oleophilic
adhesion
between cylindrical drum surfaces and ball surfaces due to the presence of
adhering
bitumen will cause the actual critical speed to be lower than what is normally
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Jan Kruyer, P.Eng. Thorsby, AB.
calculated as the critical speed of a drum. Below the critical speed the
contents
tumble inside the drum and do not remain attached to the drum wall at the top
of a
horizontal drum. The critical speed of an agglomeration drum is different from
the
critical speed of an ablation drum. In an ablation drum for producing oil sand
slurry,
bitumen adhesion normally does not have a major effect on the definition of
the
critical speed of an ablation drum since the bulk of coarse slurry solids do
not
adhering to bitumen. Thus, the critical speed of an ablation drum normally is
higher
than the critical speed of an agglomerator drum since agglomerating bitumen is
viscous and bitumen coated balls tend to stick to the cylindrical agglomerator
wall
and take more time to fall away from the wall near the top of the drum than
water
wetted coarse solids that revolve and tumble in the drum without major bitumen
adhesion. The critical speed for an agglomerator drum is defined in these
specifications as the surface speed of the inside cylindrical wall of the drum
at which
balls of specific gravity in excess of 3 and larger than one centimeter in
average size
remain adhering at all times to the inside cylindrical wall of the drum in the
presence
of bitumen at the operating temperature of the drum contents. Below the
critical
speed the bed of balls tumbles inside the rotating drum. For an ablation drum
the
critical speed is defined as the surface speed of the inside cylindrical wall
of the drum
at which water wetted gravel larger than one centimeter in average size
remains
adhering at all times to that inside cylindrical drum wall in the presence of
bitumen at
the operating temperature of the drum contents. Critical speed may be
expressed in
RPM, RPS or in surface speed of the inside drum wall for a given drum inside
diameter at a selected internal location in the drum away from the end walls.
For a
drum that is not conical in shape this internal location may be at any place
on the
inside cylindrical wall but not in close proximity to the end walls.
"cylindrical" as used herein indicates a generally elongated shape having a
circular cross-section of approximately constant diameter.
"de-bituminized" or debituminized refers to a mixture, slurry or suspension
from which bitumen has been at least partly removed.
"digested" as used herein refers to the condition of a slurry of oil sand and
water that has been ablated sufficiently to be suitable for separation into
bitumen
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Jan Kruyer, P.Eng. Thorsby, AB.
product and de-bituminized tailings effluent after oversize has been removed
before
such separation.
"endless cable" or "endless rope" is used interchangeably in this disclosure,
unless explicitly stated to the contrary, to refer to a cable or rope having
no beginning
or end, but rather the beginning merges into an end and vice-versa, to create
an
endless or continuous cable or rope. The endless cable or rope can be, e.g., a
wire
rope, a non metallic rope, a carbon fiber rope, a single wire, compound
filament or a
monofilament which is spliced together to form a continuous loop, e.g. by a
long
splice, by several long splices, or by welding or by adhesion.
"enlarged bitumen" refers to bitumen particles that have been agglomerated in
an agomerator to form enlarged bitumen phase particles or bitumen phase fluid
streamers for subsequent capture by an apertured oleophilic screen. Enlarged
bitumen may contain mineral solids.
"generally" refers to something that occurs most of the time or in most
instances, or that occurs for the most part with regards to an overall
picture, but
disregards specific instances in which something does not occur.
"fluid" refers to flowable matter. As such, fluid specifically includes
slurries,
suspensions or mixtures (continuous liquid phase with suspended particulates).
In
describing certain embodiments, the terms slurry, sludge, mixture, mixture
fluid and
fluid are used interchangeably, unless explicitly stated to the contrary. A
fluid may
be a liquid but it also may be gas. It may be a gas dispersed in liquid or a
liquid
dispersed in gas.
"multiple wrap endless cables" as used in reference to separations processing
refers to a revolvable endless cables that are wrapped around two or more
drums
and/or rollers a multitude of times to form revolving or revolvable endless
apertured
oleophilic screen belts having spaced cable wraps. Proper movement of an
endless
belt with multiple wraps can be facilitated by at least two guide rollers or
guides that
prevent an endless cable from rolling off an edge of the drum or roller, and
guide the
cable back to the opposite end of the same or other drum or roller. Apertures
of the
endless belt are formed by the slits, spaces or gaps between sequential wraps.
The
endless cable can be a single wire, a wire rope, a plastic rope, a compound
filament or
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Jan Kruyer, P.Eng. Thorsby, AB.
a monofilament which is spliced together to form a continuous loop, e.g. by
splicing,
welding, etc. As a general guideline, the diameter of the endless cable can be
as large
as 3 cm and as small as 0.01 cm or any size in between, although other sizes
might be
suitable for some applications. Very small diameter endless cables would
normally
be used for small separation equipment and large diameter cables for large
separating
equipment. A multiwrap endless cable belt may be formed by wrapping the
endless
cable multiple times around two or more rollers and/or drums. The wrapping is
done
in such a manner as to minimize twisting of and stresses in the individual
strands of
the endless cable. An oleophilic endless cable belt is a cable belt made from
a
material that is oleophilic under the conditions at which it operates. For
example, a
steel cable is formed from a multitude of wires, and the cross section of such
a cable
is not perfectly round but contains surface imperfections because of voids
between
individual wires on the surface of the cable. The same applies to a rope not
made
from metal wire. Bitumen captured by such a cable or rope may at least partly
fill the
voids between the individual wires or strands along the rope or cable surface,
and will
remain captured in those voids while the bulk of the bitumen is removed from
the
rope or cable surface in a bitumen removal zone. This residual bitumen trapped
between adjacent cable strands on the surface of the rope or cable helps to
keep it
oleophilic even after the bulk of the bitumen has been removed in a bitumen
removal
zone. This trapped bitumen serves as a nucleus for attracting more bitumen as
the
rope or cable subsequently passes through a separation zone.
"oleophilic" as used in these specifications refers to an ability to attract
bitumen upon contact. It differs from the conventional accepted term of
oleophilic
since it is selective and refers specifically to the capture of bitumen on
contact by and
the adhesion of bitumen to an oleophilic surface, to a bitumen coated surface
or to
bitumen phase itself. Most dry (not water wetted) metallic, plastic and fibre
surfaces
are oleophilic or can be made to adhere to bitumen upon contact (or are
oleophilic as
here defined). A non metallic rope, or a metal wire rope normally is
oleophilic and
will capture bitumen upon contact unless the rope is coated with an
undesirable
coating that prevents bitumen adhesion. A plastic rope or metal wire rope that
is
coated with a thin layer of bitumen normally is oleophilic, since this layer
of bitumen
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Jan Kruyer, P.Eng. Thorsby, AB.
will capture additional bitumen upon contact. A plastic rope or metal wire
rope will
not adhere to bitumen when it is coated or partly coated with light oil since
the low
viscosity of light oil will not provide adequate stickiness for the adhesion
of bitumen
to the rope. In other words, a layer of light oil on the rope surfaces may
prevent the
attachment of bitumen to the rope wraps. Therefore, such an oil wetted surface
is not
oleophilic as defined under the specifications of the present invention.
Similarly, a
rope (wire or plastic) covered with a thin layer of hot bitumen will not be
very
oleophilic as defined herein until that thin layer of bitumen has cooled down
close
enough to the process temperature to allow adequate bitumen adhesion to the
wraps
of the endless rope at the selected process temperature. Normally the process
temperature is less than 50 degrees centigrade and in some cases may be as
lower
than 5 degrees centigrade, depending on the viscosity of the bitumen phase of
the
mixture. In some mixtures, minor amounts of lighter hydrocarbons mixed in with
the
bitumen result in a major reduction in the bitumen phase viscosity at the
separation
temperature. The optimum processing temperature, therefore, is at least partly
governed by the viscosity of the bitumen phase of the mixture being separated.
When
the mixture contains a small amount of light hydrocarbon dissolved in the
bitumen
phase, processing temperature may be as low as one or two degrees above zero
degrees centigrade. In the one extreme, when the processing temperature is too
high,
or bitumen is diluted, the viscosity of the bitumen phase may be too low,
causing
bitumen phase not adhere well to the screen surfaces. In the other extreme,
when the
processing temperature is low for aqueous mixtures containing undiluted
bitumen, for
example, when approaching the freezing temperature of water, bitumen phase may
become hard and loose its tackiness and will not adhere to an oleophilic
surface.
Therefore, process efficiency is reduced when the mixture temperature is too
high or
too low. The preferred temperature is somewhere between 20 and 50 degrees
centigrade for undiluted bitumen phase.
"oleophilic sieve" is a generic name that applies to any revolving apertured
oleophilic screen, including a mesh belt, a conveyor belt, or a perforated
belt. Such a
sieve captures bitumen on the sieve surfaces in a separation zone and releases
bitumen from the sieve surfaces in a bitumen recovery zone. Years ago the
inventor
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Jan Kruyer, P.Eng. Thorsby, AB.
uses mesh belts and standard apertured conveyor belts but these did not
perform well
under long duration testing. Newer and better belts have been developed that
last
longer and are more effective. It is not unreasonable to anticipate that,even
better and
more effective oleophilic sieves will be developed in the future; all of which
will
capture bitumen phase on the sieved surfaces and allow de-bituminized aqueous
phase to pass through the sieve apertures. As used in these specifications,
oleophilic
sieve or apertured oleophilic screen may refer to a revolving or revolvable
apertured
oleophilic endless belt made from oleophilic multiple rope wraps or from
oleophilic
multiple cable wraps. Apertures in such an oleophilic sieve or screen are the
slits
between adjacent rope wraps or adjacent cable wraps. Rope or cable may be
formed
into an apertured endless oleophilic belt by means of wrapping an endless
cable
multiple times around two or more rollers or drums. Alternately, multiple
adjacent
endless cables may be supported by rollers or drums. Rope generally refers to
a non
metallic rope and cable generally refers to metallic wire cable. However, rope
as
used herein may also refer to metal wire rope. When using oleophilic cable
wraps to
separate bitumen from an aqueous mixture, water and suspended hydrophilic
solids
pass through slits or voids between sequential wraps, whilst bitumen phase is
captured by wraps upon contact in a separation zone. The captured bitumen
phase is
subsequently removed from the oleophilic wrap surfaces in a bitumen removal
zone
to become the bitumen product of separation. An oleophilic sieve may also take
the
form of an apertured endless belt not made from cable wraps, provided it can
effectively capture bitumen on its surfaces in separation zones, can
effectively release
captured bitumen from its surfaces in bitumen removal zones and is long
lasting in an
industrial environment. In due time several alternate apertured oleophilic
endless
belts may be developed that will be suitable for use in long lasting
commercial
equipment to serve as oleophilic sieves. These alternate belts are
contemplated for use
in the present invention. For that reason the term oleophilic sieve or
apertured
oleophilic screen is used in these specifications to include any revolvable
oleophilic
apertured endless belt that has surfaces to which bitumen can adhere for
subsequent
removal and apertures through which de-bituminized mixture can flow to
disposal or
reprocessing.
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Jan Kruyer, P.Eng. Thorsby, AB.
"oversize" refers to any rigid solids that approach in size the apertures of
the
apertured oleophilic screen or that approach the linear distance between
adjacent
cable wrap surfaces, and preferably refers to any solids that approach 10% of
the
linear distance between adjacent cable wrap surfaces or size of apertures.
Very large
oversize particles have difficulty passing mixture dispenser apertures that
feed an
apertured oleophilic screen and also have difficulty passing between adjacent
cable
wraps, or through belt apertures. In addition, sand particles from oil sand
ore tend to
be very abrasive and may cause damage to apertured belts, cable wraps and
distributor outlets. Such smaller particles may not block the apertures but
may cause
major abrasion damage to apertured oleophilic screen and preferably are also
removed as part of the oversize before the mixture is allowed to pass to
apertured
oleophilic screen apertures. The smaller particles of this oversize may be as
small as
sand. Therefore, any mixture of large mineral rigid particles, which may
include
abrasive sand size particles may be called oversize as defined in these
specifications.
Grizzlies and/or hydrocyclones are devices that may be used to remove oversize
from
a mixture before it is allowed to pass through an apertured oleophilic screen
or
oleophilic sieve of the present invention. One such hydrocyclone is disclosed
in
patent application 2,661,579.
"recovery" and "removal" of bitumen as used herein have a somewhat similar
meaning. Bitumen recovery generally refers to the recovery of bitumen from a
bitumen containing mixture using an oleophilic sieve or screen. Bitumen
removal
generally refers to the removal of adhering bitumen from oleophilic sieve or
oleophilic screen surfaces. Bitumen is recovered from a mixture in a
separation zone
through the adherence of bitumen to cable wraps or sieve surfaces upon
contact.
Bitumen is stripped from or removed from cable wraps or sieve surfaces in a
bitumen
removal zone. A bitumen recovery apparatus is an apparatus that recovers
bitumen
from a mixture. Bitumen must be removed from cable wraps or sieve surfaces
continuously in one or more bitumen recovery zones in order for a bitumen
recovery
apparatus to continue to work properly to capture bitumen from an aqueous
mixture
on cable wraps or sieve surfaces in one or more separation zones. The same
applies
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Jan Kruyer, P.Eng. Thorsby, AB.
to any apertured oleophilic sieve where bitumen adheres to sieve surfaces and
debituminized mixture flows through sieve apertures.
"retained on" refers to association primarily via simple mechanical forces,
e.g. a particle lying on a gap between two or more cable wraps. In contrast,
the term
"retained by" refers to association primarily via active adherence of one item
to
another, e.g. retaining of bitumen by an oleophilic cable or adherence of
bitumen to
bitumen coated balls and adherence of bitumen to bitumen coated walls of an
agglomerator. In some cases, a material may be both retained on and retained
by
adjacent cable wraps. However it is highly undesirable for oversize rigid
particles to
be retained on cable wraps or on oleophilic sieves in the present invention.
"roller" indicates a revolvable cylindrical member or a revolvable drum, and
such terms are used interchangeably herein. The drum may have an apertured
cylindrical wall and may be an agglomerator drum. On the other hand, a roller
may
also be a non apertured metal, ceramic or rubber roller.
"sieve" refers to a rugged but flexible long lasting apertured screen, and is
used interchangeably with screen unless stated otherwise. In the recent patent
applications of the present inventor, sieve generally refers to a screen
comprising
multiple adjacent wraps of endless cable to form an apertured endless belt. A
"cable
screen" is a screen formed by wraps of endless cable.
"single wrap endless cable" refers to an endless cable which is wrapped
around two or more cylindrical members in a single pass, i.e. contacting each
roller or
drum only once. Single wrap endless cables do not require a guide or guide
rollers to
keep them aligned on the support rollers but may need methods to provide cable
tension for each wrap when sequential cable wraps are of different lengths,
unless the
cable wraps can stretch, and are held in tension. Single wrap endless cables
may
serve the same purpose as multiple wrap endless cables for separations. When
multiple wrap endless cables are specified, single wrap endless cables may be
used in
stead unless specifically excluded. A cable screen may comprise multiple wraps
of
an endless cable or may comprise multiple single wrap endless cables. When
multiple wraps of endless cables are used, guides or guide rollers are needed
for each
endless cable to prevent the wraps from rolling off support drums or rollers.
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Jan Kruyer, P.Eng. Thorsby, AB.
"slurry" as used herein refers to a mixture of solid particulates and bitumen
particulates or droplets in a continuous water phase It normally is used to
describe an
oil sand ore that has been or is in the process of being digested with water
to
disengage bitumen from sand grains, resulting in an aqueous suspension of
bitumen
particles and mineral particles in a continuous water phase that may contain
chemicals. The terms "slurry", "mixture" and "suspension" are used
interchangeably
in these specifications unless specifically identified to the contrary.
"sufficient" as used herein refers to enough, but not too much. For example,
when sufficient process aid is added to oil sand during slurry preparation,
the amount
added is sufficient to achieve the objectives of preparing the slurry. In many
cases the
oil sand ore itself contains natural detergents that help to prepare the
slurry. Also,
when recycle water from a tailings pond is used in the slurry preparation
step, this
recycle water may contain residual process aid and residual detergents that
limit the
amount of process aid additions required to achieve an acceptable oil sand
slurry.
When more than sufficient process aid is added during the slurry preparation
step, the
excess may interfere with subsequent processing or may result in
emulsification of
part of the oil sand bitumen. In some cases or for some oil sand ores, process
aid is
not required at all.
"substantially" refers to the complete or nearly complete extent or degree of
an action, characteristic, property, state, structure, item, or result. For
example, an
object that is "substantially" enclosed would mean that the object is either
completely
enclosed or nearly completely enclosed. The exact allowable degree of
deviation
from absolute completeness may in some cases depend on the specific context.
However, generally speaking the nearness of completion will be so as to have
the
same overall result as if absolute and total completion were obtained. The use
of
"substantially" is equally applicable when used in a negative connotation to
refer to
the complete or near complete lack of an action, characteristic, property,
state,
structure, item, or result.
"surface speed" is the speed of movement of the cylindrical surface of a
cylindrical drum, the surface of a conical wall at a specific location on the
conical
wall or is the speed of movement of the surface of an oleophilic sieve.
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Jan Kruyer, P.Eng. Thorsby, AB.
"Tailings effluent" or tailings as used herein is debituminized oil sand
slurry
that has passed through the apertures of an apertured oleophilic screen. It
may refer to
tailings soon after these have passed through the apertures but may also refer
to
tailings that have resided in a tailings pond for a period of time.
"ultrafine mineral particles" as used herein refers to those particles that
minimize the release of water from mined oil sand fluid tailings in a tailings
pond.
These specifically are thixotropic gel forming colloidal particles, but may
also include
small oleophilic mineral particles and bi-wetted mineral particles, that are
partly
oleophilic and partly hydrophilic and normally report to the bitumen phase
during oil
sand separations by oleophilic sieving.
"velocity" as used herein is consistent with a physics-based definition;
specifically, velocity is speed having a particular direction. As such, the
magnitude
of velocity is speed. Velocity further includes a direction. When the velocity
component is said to alter, that indicates that the bulk directional vector of
velocity
acting on an object in the fluid stream (liquid particle, solid particle,
etc.) is not
constant. Spiraling or helical flow-patterns in a conduit are specifically
defined to
have changing bulk directional velocity.
"wrapped" or "wrap" in relation to a sieve, a wire, rope or cable wrapping
around an object indicates an extended amount of contact. Wrap or wrapping
does
not necessarily indicate full or near-full encompassing of the object.
As used herein, a plurality of components may be presented in a common list
for convenience. However, these lists should be construed as though each
member of
the list is individually identified as a separate and unique member. Thus, no
individual member of such list should be construed as a de facto equivalent of
any
other member of the same list solely based on their presentation in a common
group
without indications to the contrary.
Concentrations, amounts, volumes, and other numerical data may be
expressed or presented herein in a range format. It is to be understood that
such a
range format is used merely for convenience and brevity and thus should be
interpreted flexibly to include not only the numerical values explicitly
recited as the
limits of the range, but also to include all the individual numerical values
or sub-
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Jan Kruyer, P.Eng. Thorsby, AB.
ranges encompassed within that range as if each numerical value and sub-range
is
explicitly recited. As an illustration, a numerical range of "about 1 inch to
about 5
inches" should be interpreted to include not only the explicitly recited
values of about
1 inch to about 5 inches, but also include individual values and sub-ranges
within the
indicated range. Thus, included in this numerical range are individual values
such as
2, 3, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This
same
principle applies to ranges reciting only one approximate numerical value.
Furthermore, such an interpretation should apply regardless of the breadth of
the
range or the characteristics being described.
Bold text in the present disclosure is provided for convenience only.
DETAILED DESCRIPTION OF THE FIGURES
Figure 1 is a general flow diagram representing a current commercial oil
sands separation process using bitumen froth flotation. Oil sand is mined (1)
and
moved by large haulers (2) as ore (3) over a distance to a crusher (4) to
break the oil
sand into particles sizes that can flow through a slurry pipeline. A cyclo
feeder (5)
mixes slurry water (7) and air (6) with the crushed ore for introduction into
a slurry
pipeline (8). Pumps are not shown in this Figures to keep the flow diagram
simple.
The pipeline is about 10 kilometers long and the liquid in this pipeline is in
turbulent
flow to process the oil sand ore with water and air to condition it and
produce an
aerated oil sand slurry (11). The water (7) is added to the crushed ore in a
controlled
amount to produce a relatively thick slurry that will allow air to thoroughly
mix with
and become part of the slurry (11). Additional air (9) may be introduced into
the
pipeline to assist in the formation of a suitable aerated slurry. Flood water
(15) is
added near the end of the pipeline to thin the slurry prior to it entering the
primary
separation vessel (P.S.V.) (12) Aerated bitumen (16) rises to the top of the
P.S.V. and
is skimmed off to become the froth product of extraction. Middlings (17) from
the
middle of the P.S.V. join the bottoms (18) of the P.S.V. and flow to a
tailings oil
recovery vessel (T.O.R.V.) where bitumen froth (13) rises to the top and joins
the
slurry (11). Middlings from the middle of the T.O.R. flow to a hydrocyclone
(20) to
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Jan Kruyer, P.Eng. Thorsby, AB.
produce additional froth (14) that joins the froth (13) of the T.O.R.V. The
underflow
of the hydrocyclone (20) joins the tailings (22) of the T.O.R.V. to become the
final
tailings (23) of the extraction process, which flow to a tailings pond (not
shown).
Except when gravity flow is feasible, each process stream is moved by a pump
under
suitable control. This makes this a complex process that requires constant
monitoring.
While this information is not readily available, the total residence time
required to resolve oil sand ore to bitumen product and tailings may be
estimated to
required well over an hour. Residence time in the P.S.V. reportedly is about
45
minutes and residence in the T.O.R.V. may be estimated to be about 45 minutes
for a
total residence time in these two vessels of about 90 minutes to achieve
acceptable
bitumen product recovery. Bitumen recovery would be seriously reduced, and the
commercial process would be less than satisfactory if shorter residence times
were
used.
Figure 2 is a flow diagram of a proposed oil sands separation process
that uses an oleophilic Sieve in the form of an agglomerator and apertured
oleophilic
screen to separate oil sand ore adjacent to a mine face. It eliminates the
long pipeline
of Figure 1 and may be located near the mine face. Oil sand ore (40) is mined
(42) at
the mine face (41) and is fed into a multi stage crusher (43) that breaks the
oil sand
ore into large gravel size chunks and is introduced into a serpentine pipe
(44) with
water (56 and 57) to produce a slurry. This water comprises recycle water (56)
from
a dewatering conveyor and fresh make up water (57). Make up water is required
since the solid tailings (55) normally contain approxiately about 20% water
that
leaves the system with these tailings (55) but may be recovered in part
lateron. A
serpentine pipe (44) for producing oil sand slurry induces high turbulence and
impact
forces in its interior to digest oil sand ore with water. The serpentine pipe
is
described by the present inventor in pending Canadian patent application
2,638,551.
The slurry (45) enters a confined path hydrocyclone (46) which features a
coiled pipe
upstream of the hydrocyclone body. The confined path hydrocyclone is described
by
the present inventor in pending Canadian patent application 2,661,579. The
coiled
pipe of this hydrocyclone is provided with fluid inlets along its outside
lane. Fluid is
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Jan Kruyer, P.Eng. Thorsby, AB.
injected through these inlets and serves to drive dispersed bitumen particles
from the
outside lane to the inside lane of the coiled pipe and causes these to report
to the
hydrocyclone overflow (48). The coiled pipe may be of constant curvature or of
progressively increasing curvature in the direction of flow. The fluid (47)
used in this
Figure may be air, wash water, gas, or gas dissolved in water. Additional make
up
water (49) may be provided but normally is not required nor desired since the
slurry
(45) of Figure 2 is more fluid than the thick slurry produced in the slurry
pipelines or
in the conditioning drums of conventional oil sands plants. In a commercial
bitumen
froth flotation plant the slurry must be thick enough to capture air bubbles.
Flood
water is then added in the conventional flotation plant to thin the slurry so
that aerated
bitumen can rise to the top of separation vessels past settling gravel, sand
and silt.
The slurry used for sieving by an oleophilic sieve normally is thinner than
the slurry
produced in the slurry pipeline but normally is thicker than the flooded
slurry used in
the P.S.V. of a conventional plant.
Gravel and coarse sand leave the hydrocyclone (46) as underflow (55) and are
deposited at a desired location (54) on the dewatering conveyor (53) and
dewater on
the dewatering conveyor (53). The underflow is relatively coarse and dewaters
rapidly to produce recycle (56) water that flows down the incline of the
conveyor
while the coarse solids move up the incline of the slowly moving conveyor
(53). The
overflow (48) from the hydrocyclone (46) enters an agglomerator (59) that has
an
oleophilic sieve (62) wrapped around the apertured cylindrical wall of the
agglomerator. The sieve may comprise multiple cable wraps to form a, sieve
that has
longetudinal members but no cross members. This oleophilic sieve apparatus and
method is described by the present inventor in a number of pending Canadian
patents
including 2,638,596 and 2,638,474 and 2,653,058 and 2,666,025 and 2,690,951.
In
Figure 2, the oleophilic sieve is illustrated in the form of a revolving drum
(59) with
apertured cylindrical wall (50) where cable wraps are in close proximity to
the drum
apertures to allow capture of bitumen by the cable wraps as de-bituminized
aqueous
phase of the slurry passes between the cable wraps to disposal as fine
effluent (52).
Bitumen product (51) is removed from the moving cable wraps in a bitumen
removal
zone (58). The drum is not immersed but a baffle (51) is provided to manage
the fine
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Jan Kruyer, P.Eng. Thorsby, AB.
effluent (52) that leaves the oleophilic sieve (59) and direct it to a desired
location
(55) on the dewatering conveyor (53). Water from the fine effluent (52) flows
down
the incline of the conveyor and is filtered by the coarse underflow (55)
deposited on
the moving conveyor at the chosen location (54) before this water becomes part
of the
recycle water (56). The effluent fines (52) contain fine sand, silt, and clay.
The
coarser fractions of the fine effluent (52) reports to the moving conveyor
(53) but
water and the finer fraction of the effluent (52) is filtered by the coarse
and fine
deposit on the top flight of the conveyor before it reports to the recycle
water (56).
Since the top flight of the conveyor (53) moves upward, dewatered solid
tailings (55)
containing about 20% water, fall off the conveyor and are discarded. Upon
standing
these discarded tailings may release some additional water which can be used
as part
of the process water (57) but this water will have cooled, while recycle water
(56)
from the conveyor (53) will contain heat content not yet lost to the
environment. Hot
water may be used for the supply of make up water (57) to maintain a desired
slurry
(45) temperature which normally is between 20 and 50 degrees centigrade for
oleophilic sieving of oil sand ore slurries.
In the above referenced pending patents of the present inventor, and in his
expired patents, a wide range of oleophilic sieve configurations and methods
are
described. Any one of these configurations may be used for and fitted in as
the
oleophilic sieve of Figure 2 if suitable and desired. In all cases the sieve
involves a
revolving apertured oleophilic screen and may use cable wraps of metal or
plastic
rope. The mesh belts and industrial apertured conveyor belts disclosed for
that use in
the expired patents by the present inventor did not last long enough or are
not as
effective for separations as the more recent cable belts of his pending
patents.
One feature of the dewatering conveyor is that it preserves some of the
process heat content into the recycle water, since the dewatering process here
described results in a relatively warm recycle water and reduces the demand
for
additional heat to form the slurry.
Hydrocyclones may be used instead of dewatering conveyors (53) to dewater
the fine effluent (52). The coarse underflow from such hydrocyclones may be
deposited temporarily on an inclined slab to allow water to run off before the
coarse
CA 02700446 2010-04-22
Jan Kruyer, P.Eng. Thorsby, AB.
tailings are used for oil sand site reclamation purposes. Furthermore, coarse
tailings
(55) may be mixed with underflow from hydrocyclones when hydrocyclones are
used
to dewater fine effluent (52) for reclamation purposes.
Figure 3 is a flow diagram very similar to the flow diagram of Figure 2 but it
includes a number of optional features that take advantage of modifications
possible
when an oleophilic sieve is used to separate mined oil sand ore. In this case
the
serpentine pipe is replaced by a cateracting high speed ablation drum (73) to
digest
crushed oil sand ore with water. In the prior art of oil sand separation using
bitumen
froth flotation, conditioning drums are or have been used instead of slurry
pipelines to
ablate the oil sand ore with water and condition it to become a slurry. These
conditioning drums require careful control of slurry water content and drum
rotation,
speed to encourage the capture of air into the slurry before it is flooded
with water
and introduced into the P.S.V. However, the oleophilic sieve does not require
the
capture of air into the slurry. It does not require careful control of the
water content
of the slurry to keep it thick before it is flooded, since it does not flow
into a P.S.V.
As shown in Figure 3, all the required water for producing and separating an
oil sand
slurry is add to the oil sand ore at the beginning, after it is crushed. The
crushed ore
and water enter a high speed ablation drum rotating rapidly. In some cases the
rotation rate may be as high as 80% of the critical RPM but it may be as low
as 30%
of the critical RPM when lifters are used in the drum as described with Figure
4. The
interior is provided with strong longitudinal flights (not shown in Figure 3)
that lift
the drum contents and are designed to stand up to internally falling or
cateracting
rocks and gravel that form part of the crushed ore. These rocks and gravel,
coming
from the mine face, assist in digesting the slurry by pounding the oil sand
ore and
pulverizing the oil sand in the presence of an abundance of water to form a
slurry that
is screened by a grizzly (78) to remove rocks, and gravel from the slurry
leaving the
drum (73). This grizzly (78) may be a single grizzly or may consist of a
number of
grizzlies in series to remove rocks and gravel from the slurry of
progressively smaller
solids dimensions. The oversize may be washed with water and this wash water
may
be added to the slurry feed (76) for the hydrocyclone (77). Overflow (81) from
the
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Jan Kruyer, P.Eng. Thorsby, AB.
hydrocyclone (77) flows to the agglomerator and oleophilic screen as in Figure
2 but
the underflow is temporarily deposited onto a slab that forms a membrane (90)
and
allows the collection of water run off (75) that may be used as recycle water
to
produce more slurry. Fine aqueous effluent (87) flows over the top of the
solid
tailings (89) and allow it to filter through the solid tailings to capture
fines in the
voids between the sand grains of the solid tailings. The water run off (75)
will
contain fine silt and clay but, as shown in Example 1, these fine solids do
not interfere
in slurry separation by an oleophilic sieve, especially when steady state
fines content
is achieved in the water run off (75) due to the capture of fines in the voids
between
sand grains of the solid tailings (91). Like the top flight of the conveyor of
Figure 2,
the membrane (90) of Figure 3 collects and dewaters both coarse and fine
tailings.
Normally a larger amount of tailings collect on the membrane (90) than on the
conveyor and more heat is lost from these tailings than from the conveyor of
the
previous Figure. The membrane may be horizontal or may be sloped, and earth
moving equipment may be used for the removal of the dewatered tailings. As in
Figure 2, an oleophilic sieve separates the hydrocyclone overflow into bitumen
product (84) and effluent (87). A hydrocyclone may also be used to dewater the
effluent (87) to yield water run off (75) from its overflow while its
underflow may
join the underflow (86) of the confined path hydrocyclone to produce
additional
recycle water run off (75)
Figure 4a is an isometric drawing of a cateracting drum for producing an oil
sand slurry for the present invention. The cylindrical drum wall (104) is
supported on
slewing rings (103 and 105) in contact with driven rollers (not shown).
Crushed oil
sand ore and water enter the drum through an entrance (100) which is connected
to
the drum through a seal (101) in a drum end wall (102). The oil sand ore,
water and
the resulting digested slurry normally fills 30 percent or more of the drum
volume.
Slurry leaves through an exit (107) in the opposite end wall (106). Lifters
(108) are
mounted longitudinally on the drum interior cylindrical wall (111) and baffles
(109)
mounted on or adjacent to the lifters (108) slow down the flow of undigested
oil sand
ore through the drum but readily allow the flow of digested slurry through the
drum
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Jan Kruyer, P.Eng. Thorsby, AB.
from entrance to exit. A plow (not shown) lifts the slurry near the exit end
wall (106)
of the drum and transfers it to the exit (107). Hardened teeth (110) may be
mounted
in the drum inside to break oil sand lumps cateracting in the drum. No slurry
is
shown in this Figure to keep the drawing simple. Current conventional oil sand
conditioning drums have a length to diameter ratio between 5 and 6. A
cateracting
slurry drum of the present invention has a length (L) to diameter (D) ratio
between 1
and 3.
Figure 4b is an inside view of the drum of Figure 4a through section A-A of
Figure 4a. The cylindrical drum wall (104) is supported by sets of slewing
rings
(105) that mate with sets of rollers (116). The slewing rings (105) may be
supported
circumferentially by at least two sets of rollers (116) mounted far enough
apart to
keep the drum from jumping off its roller supports. However, since a
cateracting
drum turns rapidly and is exposed to major unbalanced stresses, three or four
sets of
mounted rollers in contact with the slewing rings normally will provide for
more
effective containment of the drum on its supports. The direction of drum
rotation is
shown with the arrow (115) and lifters (108) are shown in end view. Rollers
(116)
may be flanged to keep the slewing rings and drum in proper alignment while
shafts
(117) position the rollers. Dashed lines (114) show the radial contact surface
of the
rollers ( 116). Baffles (109) slow down the flow of undigested oil sand lumps
through the drum from entrance to exit. Slurry can pass under the baffles but
undigested oil sand lumps do not readily pass by these baffles (109) except in
the cut
out portion (113) of the baffles. These cut out sections of the baffles allow
the flow
of undigested oil sand, rocks and undigested clay through the drum but at a
reduced
rate. Dotted lines (120 and 121) show the cateracting flow of oil sand slurry
and
undigested oil sand lumps and rocks inside the rotating drum. The open arrows
(122)
illustrate the direction of flow. Hardened teeth (123) may be mounted inside
the
drum to catch and break up oil sand lumps that fall or flow down into the
slurry due
to the cateracting activity in the drum. The lower dotted lines (120) give an
indication of the cateracting flow of the oil sand and water mixture in the
drum when
lifters (108) are not present and the drum rotates at cateracting speed, or
when the
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Jan Kruyer, P.Eng. Thorsby, AB.
drum rotates at a lower speed and the lifters (108) help to induce cateracting
of the
drum contents. The upper dotted lines (121) give an indication of the
cateracting flow
of the oil sand and water mixture in the drum when the drum rotates at a
faster speed
and the lifters (108) cause the contents of the drum to be lifted higher up in
the drum
before falling back down into and onto the drum contents near the middle or
bottom
of the drum. The cateracting drum of Figures 4a and b is designed to rotate at
a drum
speed that is between 30% and 80% of its critical speed. Its residence to
produce an
acceptable slurry for separation by an agglomerator and oleophilic sieve is
less than 3
minutes and in some cases may be considerably less than 2 minutes.
In most cases a process aid, such as sodium hydroxide is not required to
produce a properly digested slurry in the processes of Figures 2 and 3.
However in
some cases the use of a process aid is desired. It is the objective of the
present
invention to allow the use of a suitable process aid, such as sodium
hydroxide,
sodium carbonate sodium silicate, calcium hydroxide or calcium sulphate when
that
process aid will help in the production of a suitably digested oil sand
slurry.
SPEED OF SEPARATION
As mentioned above with reference to Figure 1, the residence time in the
conventional P.S.V. is approximately 45 minutes in the T.O.R.V. vessel another
approximately 45 minutes for a total of 90 minutes in these two vessels,
ignoring for
simplicity sake the hold up in the various recycle loops illustrated in Figure
1. The
only bitumen recovery device used for the present invention is the
agglomerator with
its surrounding apertured oleophilic screen illustrated in Figures 2 and 3.
Tests were
conducted in a pilot plant with a screen similar to Figure 2. It used a drum
1.108
meters in diameter and 0.095 meters in length to keep the pilot plant small
enough to
conserve feedstock and yet yield acceptable pilot plant results. The feed rate
of
bitumen containing mixture was 2 cubic meters per hour and the bitumen content
of
the aqueous mixture was 6.07 wt%. The drum was filled to 50% of its volume
with
bitumen coated balls, with voids between the balls. Bitumen filled a large
portion of
the voids between the ball surfaces. About 10% of the drum volume was air as
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CA 02700446 2010-04-22
Jan Kruyer, P.Eng. Thorsby, AB.
determined by the level of de-bituminized mixture in the apertured drum,
observed
flowing out of the upper drum apertures not covered by the oleophilic screen.
The
upper portion of the drum was not covered by the screen and mixture could flow
out
of the drum when this level became too high, and then conveniently flowed down
the
drum wall and passed through the screen apertures. However, the feed rate into
the
drum was controlled to minimize flow through the uncovered drum apertures. As
a
result, the separating feed mixture in the drum occupied approximately 40
percent of
the drum volume during separation. Based on these data, the mixture volume in
the
drum during separation was 0.4(it)(1.108)(1.108)(0.095)=0.147 cubic meters and
the
flow rate was (2)/60= 0.0333 cubic meters per minute, resulting in a residence
time of
(0.147)/(0.0333)= 4.4 minutes. Dividing this into 90 minutes results in a
separation
rate by the apertured oleophilic screen that is about 20 times as fast as
froth flotation.
However this is a comparison between pilot plant data and commercial data and
may
not take into account all the variables between the two separation methods.
However
it is reasonable to assume from the above findings the very encouraging and
unexpected result that oil sand separation using an apertured oleophilic
screen is an
order of magnitude faster than oil sand separation that uses conventional
froth
flotation methods. Not only is the process faster but it requires fewer flow
loops and
is more energy efficient. Another major difference is that a high speed
ablation drum
(73 of Figure 3) may be used to prepare the slurry; a drum that is much
smaller and
faster than the gentle conditioning drums of commercial plants that required
slow
rotation rates to capture air in the thick slurry before water flooding. The
high speed
ablation drum can handle a higher water content in the rapidly rotating
slurry,
resulting in faster slurry preparation but without air entrainment in the
slurry. Since
the oleophilic sieve does not require air in the slurry, this is not a
problem. A fluid,
such as water, air, gas or gas dissolved in water is used in small amounts in
the
process of Figures 2 and 3 to drive residual bitumen to the inside lane of the
confined
path upstream from the hydrocyclone (46) or (77) body of the respective
Figures. It
scavenges for finely dispersed bitumen and serves to collect an increased
amount of
bitumen in the hydrocyclone overflow being fed to the oleophilic sieve and,
reduces
or eliminates bitumen in the underflow of the hydrocyclone.
CA 02700446 2010-04-22
Jan Kruyer, P.Eng. Thorsby, AB.
While sieving of a slurry in a pilot plant may take only 4 minutes, Residence
time in a commercial plant may take longer, such as 7 minutes, due to the
choice of
equipment, the need for safety and the need for additional pumps and piping,
etc., but
is not expected to exceed 20 minutes.
PRIOR ART
In Canadian patent 2,029,795 Cymerman discloses the use of pipelines to
convert mined oil sand and water into oil sand slurry. For comparison purposes
he
provides information on existing conventional conditioning drums in use by
industry
to prepare oil sand slurry for separation. These drums are still in use to
produce oil
sand slurry for separation but newer separation plants use the slurry
pipelines
proposed by Cymerman. According to the supplied information, a typical
commercial
conditioning drum is 30.5 meters long and 5.5 meters in diameter, for a drum
volume
of (,n)(5.5)(5.5)(30.5)/4 = 725 cubic meters. The oil sand feed rate to the
drum is 4500
metric tons per hour, which at a specific gravity of 2.1 is 2143 cubic meters
per hour.
Water at 95 centigrade and liquid process aid added to the drum add another
1105
tonnes per hour to the drum, which at a specific gravity of 1.0 is 1105 cubic
meters,
for a total feed rate of 3248 cubic meters per hour entering the 725 cubic
meter drum.
The stated residence time in the drum to produce an acceptable slurry is 3
minutes, or
1/20 hour. Based on that information, the percentage fill of the conditioning
drum is
(100)(3248)/(725)/(20)=22.4%. The water content of the tumbler produced slurry
may be computed when it is assumed that oil sand ore contains about 4.0 wt%
water,
11 % bitumen and 85% solids. The resulting slurry produced per hour then
contains
3825 metric tons of solids (67.7%), and 495 metric tons of bitumen (8.8%) and
1330
metric tons of water (23.5%). This slurry is kept thick on purpose to capture
air
bubbles, which would not be captured if the slurry were much thinner. Then
2000
metric tons of flood water are added to this slurry per hour to yield a thin
slurry that
contains 50% solids, 6.5% bitumen and 43.5% water before it enters the
separation
vessels. (P.S.V, T.O.R.V. , etc.) This information provides a basis for
comparison for
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Jan Kruyer, P.Eng. Thorsby, AB.
the present invention and was computed from the Cymerman patent which was
based
on factual commercial oil sand separation plant data.
In Canadian patent 1,141,318 the present inventor disclosed a conditioning
drum that contains oleophilic surfaces which serves to convert a feed of water
and
mined oil sand into a slurry but which also, in the same drum, agglomerates
the
bitumen particles by means of oleophilic drum surfaces to cause small bitumen
particles to become larger for subsequent capture by an oleophilic sieve. This
drum
serves the dual purpose of slurry production and bitumen agglomeration and
therefore
the residence time in this drum was considerably longer than if slurry
production
were the only purpose. This is illustrated in Example 1 of that patent based
on pounds
and feet. The pilot plant drum size is 3 feet long and 2 feet in diameter for
an internal
volume of (n)(2)(2)(3)/4 = 9.4 cubic feet. One thousand pound of wet oil sand
per
hour containing 80.5% solids, 7.5% bitumen and 12.0% water were fed into the
drum
along with 100 pounds of water at 60 F and 50 pounds of steam at 5 psi.
Assuming
that the wet oil sand had a specific gravity of 2.0 and water and condensed
steam had
a specific gravity of 1.0 allows us to reconstitute the data from this patent.
The
volume of oil sand feed is (1000)/(62.4)/2 = 8.1 cubic feet per hour and the
volume of
water and steam added is (150)/62.4 = 2.4 cubic feet for a total of 10.5 cubic
feed
entering the drum per hour. The drum rotates at 10 RPM. Critical speed for
this
drum is (2936/1)05 = 54 RMP, indicating that it turns at 18.5% of critical
speed.
Residence time of slurry in this drum is not detailed in this patent but it
may be
computed from the slurry volume in the drum, which was between 35 and 40% and
which also is verified in Figures 3 and 4 of that patent. Slurry filling 37%
of the
drum volume represents a slurry volume at all times in the drum of (0.37)(9.4)
= 3.5
cubic feet, and comparing this with 8.1 cubic feet per hour of slurry flow
results in a
residence time of 0.43 hours or 26 minutes of residence time to achieve both
slurry
preparation and bitumen agglomeration. Since patent 1,141,318 was granted,
major
strides were made in speeding up slurry preparation and bitumen agglomeration.
To
achieve an improvement, slurry preparation and bitumen aglomeration were
thereafter
disengaged from each other. Separate drums of different drum designs were
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Jan Kruyer, P.Eng. Thorsby, AB.
developed for slurry preparation that were different from drums developed for
bitumen agglomeration. This improved and reduced processing time in both.
In Canadian patent 1,134309 Tchernyak discloses the use of steam sparging
tubes and sparging valves in oil sand conditioning drums to properly introduce
steam
into the slurry being produced. He refers to Canadian patent 918,588 where
Marshall
et. al. disclose conditioning drums that use steam to produce a slurry from
oil sand
ore and water. That patent does not provide an indication of the RPM of the
drum. It
describes the need for steam and uses a steam distributor valve and perforated
steam
ducts to inject steam into the slurry. It also mentions, but does not claim
feed flights
with sharp edges near the entrance of the drum to force the oil sand into the
drum
interior.
A major difference from the prior art is that steam is not used in the slurry
preparation drum disclosed in the present invention. The slurry preparation
drum is
smaller, turns faster and requires less time to produce the slurry; and the
slurry is
thinner than conventional commercial oil sand slurries before flooding.
AT THE MINE FACE
Current commercial oil sand mining equipment moves as the mine face
recedes and conventional commercial earth movers transport the surface mined
oil
sand to a crusher, as shown in Figure 1. From there, a long slurry pipeline
transports
the mined ore and water over a long distance to the extraction plant where it
arrives as
a conditioned and aerated slurry suitable for flooding with water and
separation by
bitumen froth flotation in P.S.V and T.O.R.V. vessels which require long
residence
times and large equipment. The current commercial oil sand separation plants
are too
large and heavy to allow these to be moved with the receding mine face, but
the
mining equipment has to move with the mine face. Because of that reality,
conversion of oil sand to bitumen is an expensive process.
However the present invention provides for separation equipment that is an
order of magnitude smaller than the size of current commercial froth flotation
extraction plants and thus may allow the use of extraction plants that move
with the
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Jan Kruyer, P.Eng. Thorsby, AB.
mine face. Unlike the required huge tailings ponds of the current commercial
plants,
the process of the present invention eliminates the need for tailings ponds
and allows
reclamation of the oil sand site on a continuous basis as portions of the oil
sand lease
are mined out.
As shown in the following example, oil sand separation by the process of
bitumen sieving from slurry is highly tolerant of fines in the process water.
Filtering
of the process recycle water through tailings sand results in a stream of
process water
in which the fines content remains constant. The fines are continuously
captured in
the voids of the tailings sand. By this method, oil sand tailings ponds may be
eliminated and site remediation may start as soon as only a portion of an oil
sands
lease has been mined out. All this is possible because sieving bitumen from
oil sand
slurry is very tolerant of process water fines content.
EXAMPLE
The results of processing of oil sand ore are shown in the following example
in kilograms. The present inventor obtained these data during a small-scale
research
pilot plant program to evaluate the merits oleophilic sieving of low-grade oil
sands.
Kilograms Total Bitumen Minerals Water
Feedstock 1929 175 1654 100
Product 363 167 79 117
Fresh water 508
Recirculation water 391 1 85 305
Oversize reject 28 1 24 3
Tailings 2007 2 1553 452
The ore was dry screened and oversize was removed from the feed before
separation of the undersize. Load cells were used to accurately measure each
stream.
Total in was 2828kg. Total out was 2796kg. Considering experimental error,
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Jan Kruyer, P.Eng. Thorsby, AB.
sampling of the streams for analyses, and water evaporation accounted for
about 30 to
40 kg during the 7 hour run.
Based on these pilot plant data of processing screened ore that contained 9.1%
bitumen, the bitumen recovery was 95.4% and the bitumen product contained
46.2%
bitumen, 21.7% solids and 32.1 % water. The recirculation water contained 22%
mineral fine solids, which did not interfere with the 95% efficient oleophilic
sieving
process but resulted in an increase in the fines content of the product. No
attempts
were made at that time to wash the bitumen product and reduce its minerals
content.
The tailings were "dry tailings" containing 22.5% water and the recycle water
was
tailings run off water that was returned immediately and continuously to the
separation process.
Total water content of the slurry was (100+508+305) = 913 kg and total solids
and bitumen content was (1654+175) = 1829 kg, for a total of 2742 kg,
resulting a
slurry water content of (100)(913)/2742 = 33.3 % which is about mid way
between
the conventional thick aerated slurry coming from a conditioning drum and the
conventional flooded slurry that is sent for bitumen froth flotation to the
P.S.V. and
T.O.R.V.
The pilot run lasted 7 hours. Runs longer that 7 hours in duration might have
resulted in minor changes in the solids contents of the recycle water.
However, this
depends on the efficiency of recycle water filtering through tailings sand and
the
transfer of fines interstitially to the voids of the tailings sand.
Expectedly, this
transfer of solids from the recycle water to the tailings sand voids will vary
with
various grades of oil sand feedstock. Using recycle water in this manner saves
on
energy requirements since the water is recycled before it cools significantly.
A
conveyor belt similar to the conveyor of Figure 2 was used for dewatering the
tailings
and for filtering the recycle during this test run. However the tailings
dewatering
method of Figure 3 may be used instead.
An important promise of the present invention is that the methods and
equipment described herein involve fewer fluid recycle loops and require a
lower
degree of equipment and operator control of the separation process than is
used or
required in the current commercial oil sands plants. The lack of recycle loops
is
CA 02700446 2010-04-22
Jan Kruyer, P.Eng. Thorsby, AB.
obvious from a comparison between Figure 1 versus Figures 2 and 3. In an
industrial
process, each recycle loop tends to adds to the complexity and cost of a
separation
plant, since each may need one or more pumps, level and flow controls and
stream
sampling and composition controls; and with an attendant demand for expert
operator
involvement.
Of course, it is to be understood that the above-described methods,
arrangements and uses are only illustrative of the application of the
principles of the
present invention. Numerous modifications and alternative arrangements may be
devised by those skilled in the art without departing from the spirit and
scope of the
present invention and the appended claims are intended to cover such
modifications
and arrangements. Thus, while the present invention has been described above
with
particularity and detail in connection with what is presently deemed to be the
most
practical and preferred embodiments of the invention, it will be apparent to
those of
ordinary skill in the art that numerous modifications, including, but not
limited to,
variations in reagent addition, concentration, temperature, size, materials,
shape,
form, function and manner of operation, assembly and use may be made without
departing from the principles and concepts set forth herein.
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