Note: Descriptions are shown in the official language in which they were submitted.
CA 02696181 2010-03-12
M. Jan Kruyer P.Eng. Thorsby, f4lberta
CALCIUM SODIUM BALANCE IN OIL SAND
SLURRY OLEOPHILIC SEPARATIONS
RELATED APPLICATIONS
This application is related to Canadian Patent Application number 2,66,025
filed
19 May 2009 entitled "Pond Sludge Bitumen and Ultra Fines Agglomeration and
Recovery ", number 2,661,579 filed 9 April 2009 entitled " Helical Conduit
Hydrocyclone Methods, number 2,638,551 filed 7 August 2008 entitled
"Sinusoidal
Mixing and Shearing Apparatus and Associated Methods ", and number 2,638,596
filed
6 August 2008 entitled "Endless Cable System and Associated Methods ".
FIELD OF THE INVENTION
The present invention relates to methods for processing oil sand ore with
water.
Methods are disclosed and claimed for digesting oil sand ore to slurry in the
presence of
water and process aid sufficient to disengage bitumen particles from oil sand
minerals in
an aqueous medium and to disperse the slurry particulates. After digesting the
oil sand
ore, enough multivalent cations are added to the slurry to replace monovalent
cations on.
surfaces of mineral ultrafines in said slurry. This selective cation
replacement on mineral
surfaces causes capture of ultrafines by bitumen phase during separation of
the slurry by
sieving through an oleophilic sieve. In this separation, bitumen agglomeration
is
followed by adhesion of bitumen phase to oleophilic surfaces of the sieve
whilst
debituminized slurry passes through apertures of the sieve to disposal as
tailings.
Accordingly, the present invention involves the fields of process engineering,
chemistry,
physical chemistry and chemical engineering.
BACKGROUND OF THE INVENTION
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Aft- Jan Knryer, P. Eng. Thorsby, fllberta
In the present invention, bi-wetted solids and mineral ultrafines are captured
by
bitumen and removed from oil sand slurries so that fluid tailings effluent,
resulting from
the process of the present invention, contain an insufficient amount of
ultrafines to form
colloids and thixotropic gels that normally prevent dewatering of conventional
oil sand
fluid tailings. The objective of the present invention is to maximize the
amount of
valuable bitumen recovered from oil sand slurries while minimizing the amount
of
ultrafines reporting to the tailings.
The instant invention is a companion to Canadian patent application 2,66,025
that
was filed on May 19th 2009, less than a year ago, which does not teach the
processing of
oil sand ore to recover bitumen. It teaches and claims the processing of oil
sand fluid
tailings that are the result of conventional commercial oil sand processing
methods that
use bitumen froth flotation. Froth flotation employs the use of air bubbles in
flotation
settling vessels. In that conventional process, bitumen particles attached to
air bubbles.
Most of that bitumen rises to the top of flotation vessels for removal as
product, leaving
some residual bitumen in the tailings. The tailings of that process are
deposited on the
shore of a tailings pond. There these tailings separate into two components,
coarse sand
that is used for tailings pond dyke building, and fluid tailings that flow
into the pond for
settling and compaction. Most of the residual bitumen arriving at the pond.
shore reports
to the fluid tailings. Natural compaction of fluid tailings may take hundreds
of years
before these tailings can be used for oil sand site remediation.
Application 2,66,025 teaches the processing of conventional oil sand fluid
tailings
and its precursors, such as middlings, that contain residual bitumen. It does
not claim the
processing of oil sand ore slurries, which normally contain more valuable
bitumen than
conventional fluid tailings. This prior application teaches the capture of
ultrafines into the
residual bitumen of conventional oil sand aqueous mixtures that are the result
of bitumen
froth extraction of oil sand ore. It is not the main objective of that
application to produce
a valuable bitumen product, but rather to use the residual bitumen found in
these mixtures
and fluid tailings to capture ultrafines. After such capture, the
bitumen/ultrafines product
would normally be discarded since tailings pond residual bitumen usually
contains acidic
components that corrode and play havoc with refinery equipment when such
bitumen is
not discarded but is upgraded to synthethic crude oil. For all intends and
purposes, this
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Mr Jan Kruyer, P.Eng. Thorsby, Alberta
residual bitumen is considered lost bitumen and may possibly have some
redeeming
value when used for the production of asphalt. It has a lower commercial value
than
bitumen recovered from mined oil sand ore. Hence production of bitumen from
the
effluent of conventional bitumen froth flotation for upgrading is not the
primary objective
of that prior application. Its primary objective is the removal of ultrafines
from
conventional fluid tailings to enhance subsequent debituminized fluid tailings
compaction
and to use the residual bitumen contained in the fluid tailings to achieve
that objective.
In contrast, the bitumen product and the tailings effluent of the present
invention
have not been associated in any way with froth flotation in a settling vessel.
The present
invention teaches the collection of ultrafines into the bitumen phase of mined
oil sand
slurries by agglomeration. After that the slurry is separated into bitumen
product and
tailings effluent. It is the primary objective of the present invention to
produce a
valuable bitumen product from oil sand ore by sieving its slurry. Its
secondary objective
is to reduce the amount of ultrafines reporting to the tailings effluent.
The prior application has introduced the problems resulting from the
accumulation of colloidal gel forming ultrafines in tailings pond fluid
tailings that result
from separations by bitumen froth flotation. The present invention teaches and
claims
methods to maximize the amount of upgradable bitumen product recovered while
reducing the concentration of gel forming ultrafines in the resulting
effluents of
separation by an oleophilic sieve.
CANADIAN OIL SANDS EARLY DEVELOPMENT
The Province of Alberta, Canada contains one of the largest hydrocarbon
reserves
in the world in the form of oil sands; a deposit consisting of sand grains,
each covered
with a thin envelope of water, with the voids between these sand grains filled
with
bitumen, a heavy hydrocarbon with a specific gravity of about 1.0 at ambient
temperature. Fine clay particles, including nano size particles are present in
the voids
between these sand grains and inside the water envelope. Oil sand deposits
that are close
to the earth surface in the Fort McMurray (Alberta) area are recovered by
surface mining
methods using very large size mining equipment to quarry the oil sand ore,
after which it
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M. Jan Kruyer P.Eng. Thorsby, fllberta
is mixed with water and air to condition it and then to recover the desired
bitumen by
froth flotation in the current commercial process.
During early commercial development, oil sands ore was mixed with steam and
caustic soda in 80 C water and gently agitated and aerated within tumblers,
with a
residence time of about 3 minutes prior to oversize removal. This was followed
by air
induced flotation to separate the contained bitumen in the form of a froth.
The aerated
bitumen rose to the top of froth flotation vessels. Hydraulic transport, a
process of
slurrying oil sands ore such that it can be transported via pipeline was
developed later to
obviate the need for expensive long distance conveyor belts, that were needed
prior to
that to transport the ore between mine site and extraction plant. Hydraulic
transport also
allowed a reduction of process temperatures to about 50 C but required
crushing of the
oil sand ore before introduction into the pipeline. Current commercial
operations can
now produce bitumen froth from flotation vessels, operating in this 50 C
temperature
range, after the oil sand slurry has been conditioned in a slurry pipeline.
Conditioning is
a term used to describe a chemical/mechanical process wherein water,
monovalent
cations and detergents disperse the oil sand ore so that bitumen is disengaged
from the
solid mineral particles. The disengaged bitumen droplets adhere to air bubbles
and create
a froth that rises to the top of flotation vessels, recovering most of the oil
sand bitumen.
However, some bitumen particles are too small or are weighted down by small
mineral
particles and never rise to the top of flotation vessels in the allowed
processing time.
Several parameters are known to affect the extent of conditioning. These
include
oil sands ore facies, bitumen and fines content, clay type, process chemical
additives,
process water quality and chemistry, and process parameters such as
conditioning
temperature, slurry density and conditioning time. Hydrotransport of oil sands
ore slurry
serves to ablate the oil sand lumps and to disengage bitumen particles from
sand grains.
At about 50 C pipeline temperatures, such lumps are almost completely ablated
after
approximately 30 min of transportation, which corresponds to a pipe length of
about five
kilometers. The current commercial conditioning process of oil sand ore
required for
bitumen froth flotation involves bitumen liberation from sand particles,
dispersion of the
oil sand ore in water and attachment of bitumen droplets to fine air bubbles
to allow for
the required froth flotation. Since the density of bitumen is near to that of
water, bitumen
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Mr. Jan A-ruyer, P.Eng. Thorsby, Alberta
separation must be facilitated by the use of air. Flotation of bitumen without
air would be
very inefficient and not commercially feasible. Thus, the conventional
commercial
method of recovering bitumen from mined oil sands involves mixing the oil sand
ore with
water and caustic soda to form a slurry by breaking up the mined oil sand
lumps,
enlarging the water envelope around each sand grain, and disengaging the
bitumen
particles from the sand grains at elevated temperatures. It further requires
the adhesion of
bitumen particles to air bubbles in order to achieve the separation in
subsequent froth
flotation vessels.
Process water in the current commercial process normally is a mixture of fresh
water and recycle water from the surface of a tailings pond which recycle
water contains
residual detergents, ions and ultrafine mineral particles. The amount of water
added in the
slurry production stage normally is limited to maintain a thick slurry that
enhances
capture and retention of small air bubbles in the slurry. Dilution flood water
is then added
just before the slurry enters the separation vessel(s). This dilution water
reduces the
aerated slurry viscosity and enhances bitumen flotation. Additional air
normally is
added during separation. The first separation vessel is a large thickener type
of vessel,
called a primary separation vessel (PSV), wherein bitumen froth floats to the
top, sand
settles to the bottom and fine suspended solids and finely dispersed bitumen
accumulate
in the middle of the vessel. The primary bitumen product is skimmed from the
top of the
PSV, is de-aerated, dewatered, and cleaned, and may be upgraded to synthetic
crude oil
or may be shipped to a refinery by pipeline when diluted with a light
hydrocarbon. The
sand and water product from the bottom of the PSV are the primary tailings.
These are
shipped by slurry pipeline to a tailings pond.
The middlings, removed from the middle of the PSV, contain dispersed bitumen
and mineral fines in water and are processed further to scavenge for and
recover finely
dispersed bitumen droplets with air in subaeration flotation cells or in
tailings oil
recovery (TOR) vessels. The resulting secondary bitumen product is combined
with the
primary bitumen product from the PSV. The tailings from the subaeration cells
or from
the TOR vessels are combined with the PSV bottom sand tailings and are pumped
by
pipeline to a tailings pond. At the shore of the pond, coarse sand drops out,
and is used
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Mr. Jan Kruyer P.Eng. Thorsby, 41berta
for building pond dykes; and the remaining fluid tailings flow into the pond
for settling
and compaction.
Due to the presence of chemicals added or formed during the bitumen froth
flotation separation process, dykes are required to surround each tailings
pond and
thereby contain the toxic tailings. The GCOS (Great Canadian Oil Sands)
commercial
mined oil sands plant opened around 1967, resulting in the first tailings pond
that was
built near the shore of the Athabasca river, using a dyke to prevent tailings
water from
reentering the river. In the early days, tailings and effluent were considered
to be a
harmless byproduct of oil sands mining and were thought to require only a
short storage
and settling time before tailings water could be returned to the environment.
Later it was
discovered that water from the commercial flotation process was too toxic for
return to
the river. The Alberta and Canadian governments then enacted laws to prevent
the return
of tailings water back into the environment. Subsequent court cases resulted
in legal
fines that were levied when proof was found that contaminated water entered
the natural
environment. The resulting improved dykes around Alberta oil sand tailings
ponds
became marvels of engineering that were very expensive to build and expensive
to
maintain to adequately minimize the leakage of toxic water back into the
environment.
Many reports have subsequently attested to the fact that containment of this
toxic tailings
water was very difficult to achieve, and that significant amounts of toxic
tailings water
have tended to seep out of the tailings ponds in spite of major efforts to
minimize such
seepage. New regulations by the Alberta government now require a major
reduction in
the amount of fluid tailings being stored in future in the tailings ponds.
GEL FORMATION
Biological testing has shown that tailings water from commercial froth
flotation oil sands plants, even diluted by a factor of 10 with fresh water
can kill more
than half of trout fingerlings added to this mix within 92 hours, indicating a
high degree
of tailings water toxicity. Additional tailings problems surfaced when it was
discovered
that, as a result of froth flotation physics and chemistry, the mineral nano
size fraction of
the tailings fines in these ponds tended to form non Newtonian gel like
colloidal
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Mr. Jan Kruyer, P.Eng. Thorsby, Alberta
structures that trap water, bitumen and mineral fines and thereby prevent
compaction of
clay and silt particulates once the fluid tailings in the pond reach a solids
content of about
35 percent. In the near quiescent state of fluid tailings in ponds, these
thixotropic gels
prevent further solids settling and, over the years have kept huge amounts of
water
captured in the fluid tailings. Pumping of the fluid tailings may break down
the gel like
structures, but these structures reestablish themselves within weeks after the
fluid tailings
are returned to a quiescent state.
The jelly like fluid tailings in mined oil sands tailings ponds are identified
by
several different names, such as: sludge, fluid tailings, fine tailings or
mature fine
tailings, and are the reason why oil sand tailings ponds in the Fort McMurray
area are
growing rapidly, and represent toxic problems of major proportions. As a
result, the
current commercial oil sands tailings ponds have a combined surface area
amounting to
130 square kilometers, larger than some of the natural lakes of Alberta, and
are expected
to double during the next decade. To date about 3000 million barrels of
bitumen have
been produced from mined oil sand ore, resulting in 750 million cubic meters
of fluid fine
tailings. This amount of polluted sludge could fill a ditch 17 meters wide, 10
meters
deep, and 4500 kilometers long, all the way across Canada from Vancouver to
Hallifax.
Not only do these tailings ponds tie up a very large amount of water, and are
an
environmental hazard, but also release to the environment a significant
amounts of
methane; a gas considered by the global warming community to be twenty times
as
problematic as carbon dioxide. For example, the amount of methane released to
the air
by only one of these ponds exceeds 3.5 million cubic meters per year.
Many references may be found in current oil sand literature that state or
confirm:
"A high water holding capacity of oil sand fine tailings has been attributed
to the
presence of ultrafine (<0.2 micrometer) clay fractions", or " An ultrafine
(<0.3
micrometer) component of the oil sands fines fraction is identified as having
the potential
to be the major contributor to the thickening (gelation) or sludging
phenomenon ....", or
"ultrafine gels can therefore account for 100% of the water holding capacity
of mature
fine tailings".
OIL SAND SLURRY CHEMISTRY
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A1. Jan Kruyer P.Eng. Thorsby, 41berta
In oil sand froth flotation extraction processes, caustic soda and natural
detergents
induce an electrical charge to particulate matter in oil sand slurry. This
electrical charge
serves to repel and disperse the sand grains and mineral fines and disengage
bitumen
from the sand grains but must also allow for the adhesion of bitumen droplets
to bitumen
droplets and to air bubbles. This requires a very complex balance between
attraction and
repulsion and has been the topic of years of research in bitumen extraction
from oil sands
by froth flotation. This balance involves complex interactions between solids
of a variety
of facies and surface characteristics, including water chemistry, bitumen
droplet sizes and
compositions, and gas or air bubbles sizes and compositions.
For froth flotation, too low a concentration of caustic soda and detergents
does not
adequately disperse the slurry, makes it viscous and reduces bitumen recovery
since
aerated bitumen does not rise well in a viscous aqueous slury. Too high a
caustic
concentration results in the formation of bitumen emulsions. Furthermore,
calcium ions
present in the ore or in plant process water, or recycle water tend to react
with natural oil
sand detergents and with the detergents formed from the reaction of caustic
soda with oil
sand ore, to make these detergents less effective in disengaging bitumen from
the sand
grains. Sodium chloride and other salts present in the slurry also interfere -
with the
bitumen flotation process. Furthermore, when the ultrafine mineral
particulates are not
properly dispersed by detergents, but become attached to bitumen surfaces,
these coated
bitumen surfaces will not adhere to air bubbles and too much bitumen will
leave with the
tailings of froth flotation, resulting in poor bitumen recovery. Hence, the
chemistry of
bitumen froth flotation requires a very careful balance between attraction and
repulsion of
particles in an aqueous medium and must take account of all the chemicals
present. In
the current commercial process, sand particles and clay particles preferably
are repelled
from bitumen and from air. At the same time, it is desired that bitumen
droplets should
readily and quickly attach to air bubbles while minimizing the adhesion of
sand, silt and
clay particles to air or bitumen droplets. Large losses of bitumen to the
tailings can result
in the froth flotation process when this balance is not achieved. And, when
nano size
mineral particles coat the surface of bitumen droplets, bitumen recovery by
froth flotation
is significantly reduced, since these adhering mineral particles interfere
with bitumen to
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Mr Jan f(ruyer, P. Eng. Thorsby, 4lberta
air attachment. For that reason in froth flotation, the objective is to keep
the ultrafines
suspended in the aqueous medium so that these report to the tailings.
It is not the purpose of this disclosure to provide a detailed description of
80 years
of research in the chemistry of oil sand extraction by froth flotation, since
this is not an
objective of the present invention. Therefore, the above simplified
explanation may
suffice to explain the difference between the older art of bitumen froth
flotation from an
oil sand slurry and the newer art of bitumen sieving from an oil sand slurry.
Thus, the
objective of current commercial froth flotation is to encourage nano size
mineral particles
to report to the tailings, in spite of the fact that these nano size mineral
particles have
been found to form thixotropic gels in oil sand tailings ponds that prevent to
a large
degree the desired dewatering of fluid tailings in these ponds. In contrast,
the objective
of the present invention is to capture nano size mineral particles into the
bitumen product
of oleophilic sieving and thereby minimize the ultrafines content in the
resulting tailings
effluent of sieving.
RELATED ART
A series of Canadian patents were granted to the present inventor about 20
years ago for an oleophilic sieve process that used mesh belts and apertured
drums to
capture bitumen from oil sand mixtures. The mesh belts worked effectively in
pilot
plants but disintegrated during extended test runs. The failure of these belts
in long
duration testing resulted in a complete review of the technology and indicated
the need
for more effective sieves or apertured screens that did not rely on apertured
drums alone
nor relied on mesh belts. Commercial steel conveyor belts were tested and
patented for
bitumen sieving but it turned out that, while usable for capturing bitumen in
bitumen
separation zones, these conveyor belts did not provide for the effective
release of bitumen
in bitumen removal zones after capture. These commercially available steel
conveyor
belts made from serpentine strips of steel in the form of hinges, or from
flattened steel
coils joined by cross rods, proved to be less than desirable for efficiently
separating
bitumen from aqueous oil sand mixtures. After many years of patenting
inactivity, the
more recently filed Canadian patent applications disclose and claim methods
and
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Afr Jan Kruyer, P. Eng. Thorsby, 4lberta
equipment developed to replace the fragile mesh belts (as well as to replace
commercially
available steel conveyor belts) with rugged sieves in the form of cable screen
belts made
from multiple adjacent loops of endless non metallic rope cables or endless
wire rope
metal cables.
The newly invented cable screen belts comprise very strong, flexible and long
lasting longitudinal members that are joined at the ends to make them endless.
A special
cable guide system is employed to prevent each revolving cable from running
off the
support rollers. Since the resulting belts do not have cross members,
equipment can be
designed to readily capture bitumen in separation zones and to easily remove
adhering
bitumen in recovery zones. Furthermore, the resulting system design is
flexible and
equipment can be built to be rugged and long lasting in many configurations.
The recent
group of patent applications describing new technology equipment and its
associated
methods are summarized below.
Conventional oil sand slurry pipelines require more than 3 kilometers to
properly
digest an oil sand slurry. Canadian patent application 2,638,551 entitled:
Sinusoidal
Mixing and shearing apparatus and Associated Methods, filed August 7th, 2008,
discloses a method for digesting oil sand by water in a sinusoidal pipe
section over a
much shorter distance by high turbulence. This is particularly important when
oil sand
slurry production and extraction equipment is small enough that it can move
with the
mine face. Moving a 5 kilometer slurry pipeline with a mine face is rather
difficult, but
moving a short sinusoidal pipe with a mine face is much easier.
Since a cable belt can not accommodate coarse solids, these solids must be
removed prior to separating an oil sand slurry into bitumen and tailings.
Canadian patent
application 2,638,550 entitled: Hydrocyclone and associated Methods, filed
August 7th,
2008, discloses an effective hydrocyclone for removing coarse mineral solids
and
encouraging bitumen to report to the overflow of the hydrocyclone.
Canadian patent application 2,638,596 entitled: Endless Cable System and
Associated Methods, filed August 6th, 2008, discloses an oleophilic cable belt
that is
formed by multiple wraps of one or more oleophilic endless cables supported on
rotating
drums or rollers. Prior patents of the present inventor used revolving mesh
screens and
commercial steel conveyor belts, but this current patent application
represents new art
CA 02696181 2010-03-12
Afr Jan Kruyer P.Eng. Thorsby, Alberta
and describes a much improved and rugged endless belt apertured screen (sieve)
for
removing bitumen from an aqueous slurry or suspension.
Canadian patent Application 2,647,855 entitled: Design of Endless Cable
Multiple
wrap Bitumen Extractors, filed January 15th, 2009 discloses new design
information that
was developed during pilot plant testing of the Kruyer process, and not
disclosed in prior
patents.
Canadian patent application 2,690,951 filed January 27`h , 2010 entitled
Endless
Cable Belt Alignment Apparatus and Methods for Separations teaches and claims
methods for aligning cable wraps with apertured mixture feed outlets to
improve the
effectiveness of mixture or slurry separations.
Canadian patent Application 2,653,058 entitled: Dewatering Oil Sand Fine
Tailings using Revolving Oleophilic Apertured Wall, filed February 16`",2009,
discloses
methods for processing oil sand tailings pond sludge (fluid tailings) to
capture ultrafine
mineral particles into the residual bitumen phase that is recovered from such
sludge by an
endless cable belt. This application deals with effluents of commercial oil
sands plants
and removes residual bitumen, that was not recovered during froth flotation,
from these
effluents. It transfers ultrafines into this residual bitumen and deposits
debituminized
fluid tailings in a tailings pond for more rapid settling and compaction. The
bitumen
recovered from this process may be discarded or processed. Very often residual
bitumen
found in tailings pond sludge has weathered and contains acidic components
which
makes residual bitumen processing difficult and costly. For that reason,
discarding
residual bitumen after it has captured ultrafines is an effecticve and cost
effective way to
save on tailings pond reclamation. This is because sludge( fluid tailings)
that does not
contain ultrafines will be faster and cheaper to remediate.
PURPOSE OF THE INSTANT PATENT
Canadian patent Application 2,653,058 teaches and claims the capture of
ultrafines by bitumen in fluid tailings that are the result of conventional
oil sand
extraction processes that uses bitumen froth flotation in settling vessels
with the aid of air
bubbles. It also teaches and claims the capture of ultrafines by bitumen in
precursers of
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Mr Jan Kruyer, P.Eng. Thorsby, Alberta
these fluid tailings that result from froth flotation. In the specifications
of that prior
patent application, precursers are specifically defined as bitumen containing
streams from
conventional commercial bitumen froth flotation commercial plants. This prior
patent
did not contemplate the capture of ultrafines from an oil sand slurry in a
separation
process that does not use conventional froth flotation.
CHANGING DIRECTION AWAY FROM FROTH FLOTATION
The alternate extraction method, that passes an oil sand slurry through an
oleophilic apertured wall, screen or sieve to recover bitumen instead of using
bitumen
froth flotation is called the Kruyer process. It is less sensitive to chemical
and physical
process conditions required for froth flotation, since it does not rely on
attachment of
bitumen to flotation air. It also is much faster. For example, ignoring for a
moment the
residence time in subaeration cells or TOR vessels that augment the PSV, it
takes about
40 minutes for enough aerated bitumen to rise to the top of a primary
separation vessel
(PSV) to make commercial froth flotation an economically viable commercial
process.
In comparison it takes about 4 minutes to achieve the same degree of bitumen
recovery
when the same oil sand is slurried and sieved. This represents an order of
magnitude
reduction in processing time.
Unlike a conventional PSV, sieving an oil sand slurry to recover bitumen
requires
the prior removal of coarse solids before the slurry is passed through the
oleophilic
screen. This normally is done with a hydrocyclone. One suitable hydrocyclone
is
described in detail in copending Canadian patent application number 2,661,579
filed 9
April 2009. Sieving a bitumen containing oil sand aqueous suspension normally
involves
the agglomeration of bitumen droplets to make them larger and more easily
captured by
the sieve. One method of bitumen agglomeration and screening of oil sand fluid
tailings
is described in Canadian patent applications number 2,66,025 filed 19 May
2009. A
similar method of bitumen agglomeration and screening from an oil sand slurry
is
described in Canadian Patent application number 2,690,951 filed February 23,
2010 and
in Canadian patent application number 2,647,855 filed 15 January 2009.
Furthermore,
the design and use of a modern and rugged oleophilic apertured screen or sieve
in the
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Mr Jan Kruyer P.Eng. Thorsby, Alberta
form of adjacent wraps of endless cable is disclosed in detail in Canadian
patent
application number 2,638,596 filed 6 August 2008. This group of patents
describes an
alternate system for bitumen recovery from oil sands that differs in a major
way from the
current convention commercial froth flotation process, and yet is expected to
be rugged
enough for long dueration use in a commercial plant.
Thus, it is not the objective of the present invention to improve the art of
bitumen
froth flotation in a thickener type of flotation vessel (PSV), or to process
its effluents or
bitumen containing streams. Instead, the present invention discloses and
claims the
screening or sieving of bitumen from aqueous slurries of oil sand ore. In
particular the
present invention captures ultrafines in the bitumen product of oil sand
slurry to reduce
the amount of ultrafines reporting to the tailings of such sieving. The
present invention
recovers valuable bitumen product for upgrading, and reduces the amount of
thixotropic
gel forming ultrafines in tailings of separation in an effort to reduce the
time required to
dewater these tailings.
PILOT TESTING
The Kruyer oleophilic sieve process was piloted at various feedstocks at rates
between 0.3 and 3 metric tons per hour in test runs that lasted anywhere from
4 to 500
hours in various pilot plants. Feedstocks processed included:
/ High grade oil sand ore (about 13% bitumen content),
/ Medium grade oil sand ore (about 11 % bitumen),
/ Low grade oil sand ore (about 7% bitumen),
/ Oil sand tailings from a froth flotation pilot plant,
/ Oil sand middlings from the PSV of a pilot plant,
/ Tailings pond sludge that was 10 years old,
/ Tailings pond sludge that was 20 years old,
/ Cleaning bitumen froth recovered from a commercial tailings pond,
/ Bitumen in water emulsions from in situ recovery using steam.
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Mr. Jan Kruyer, P.Eng. Thorsby, ,41berta
EXAMPLES OF BITUMEN SIEVING INSTEAD OF FROTH FLOTATION
Pilot plant tests show that using an apertured oleophilic screen or sieve to
recover
bitumen from an oil sand slurry can to a large degree eliminate the production
of non
compacting sludge. Unlike the current commercial process that uses bitumen
froth
flotation with air to recover bitumen from an oil sand slurry, screening or
sieving bitumen
from an oil sand slurry simply passes the slurry through a rugged oil
attracting
(oleophilic) apertured screen. It is a much faster process, is easier on the
environment, is
faster and is more economical. While froth flotation is a gentle process that
requires a
residence time of more than an hour to recover a commercially acceptable
amount of
bitumen, sieving bitumen from a slurry of the same oil sand only takes a few
minutes to
recover the same amount of bitumen and often is more efficient. The following
examples
provide some information on the results of oleophilic sieving.
EXAMPLE 1
A comparison test program was carried out to compare froth flotation with
oleophilic
sieving of low grade Syncrude beach sand. Samples of the same ore were used
for the
comparison. Standard pot tests were used to obtain results for froth flotation
and a pilot
plant was used to obtain oleophilic sieve results. Pot tests were carried out
by an
independent research organization (the Alberta Research Council).
Oil sand properties:
Feed Analyses Pot Test 1 Pot Test 2 Oleophilic Sieve
Wt% bitumen 6.3 6.0 6.8
Wt% solids 84.4 84.9 85.6
Wt% water 9.0 8.8 7.6
Water to feed ratio 2.3 2.4 1.7
Operating temperature 82 C 82 C 54 C
Percent bitumen recovery 12.6 20.9 64.0
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Mr Jan f(ruyer P.Eng. Thorsby, 41berta
Product wt % bitumen 4.8 6.0 43.5
Aeration required required not required
Supernatent water clear
Thus when very low grade beach type oil sand was separated, 64 percent bitumen
recovery was achieved with oleophilic sieving while an average of 17 percent
bitumen
recovery was achieved with froth flotation. The product of sieving contained
43 wt%
bitumen and the product of froth flotation averaged less than 6 wt% bitumen.
This
clearly shows the advantage of oleophilic sieving over froth flotation for
very low grade
oil sand.
EXAMPLE 2
Samples of oleophilic sieve separation of very high grade oil sand were
submitted to the
Alberta Research Council for analyses with the following results:
wt% H2O wt% mineral wt% bitumen
Original oil sand 3.9 80.7 15.3
Bitumen product 15.6 2.8 81.6
Extracted sand 21.6 78.7 0.2
Circulating water 99.0 1.0 not measurable
Bitumen recovery: 98%
As shown in this example, oleophilic sieving of very high grade oil sand
achieved
about 98 percent bitumen recovery, which is higher than published results for
froth
flotation.
EXAMPLE 3
Samples of high grade oil sand were separated by the oleophilic sieve to
determine the
amount of water required for separation, with the following results:
wt% bitumen wt% solids wt% water
Oil sand ore 13.1 83.0 3.9
Coarse oversize 10.3 81.7 8.0
CA 02696181 2010-03-12
M. Jan Kruyer P.Eng. Thorsby, fllberla
Tailings 0.5 75.1 24.4
Bitumen product 57.8 15.0 27.2
Water demand, lb of water per lb of ore processed by the sieve: 0.42
Alsands demand, lb of water per lb of ore processed by froth flotation: 0.99
In this case water demand for oleophilic sieving was less than half the water
demand for
froth flotation.
EXAMPLE 4
Tests were conducted to evaluate the effect of time on settling of mineral
particles in
bitumen product of processing oil sand ore containing by weight 7.3% bitumen,
6.7 %
mineral and 6.0% water by means of an oleophilic sieve. The bitumen product of
the
separation contained 44.2% bitumen, 24.7% mineral and 31.1 % water. On a dry
basis
this represents 64.2% bitumen and 35.8% mineral solids. Three sealed glass
sample
containers were used and the top half of each container was analyzed for
solids content
after settling. The results on a dry basis were as follows:
Percent solids in bitumen on a dry basis, results of settling
Sample zero hours 49 days@ 16 C 48 hours@100 C
1 35.9% 23.7% 7.7%
2 35.9% 24.3% 8.1%
3 35.9% 23.4% 14.5%
These results were for static settling of bitumen product at a gravitational
force of
G=1. The results open up a now option for bitumen clean up prior to upgrading.
Storing
an inventory of bitumen product for a few months in heated tanks could result
in a
relatively clean product feed for upgrading. Bitumen product sediments from
such a tank
may be washed with water and sieved to remove coarse solids and produce a
bitumen
product that may be returned to the hot settling tank. Water washing of
bitumen product
of oleophilic sieving is detailed in Example 5. Hot centifuging the bitumen
product from
oleophilic sieving at G >I 00 without the use of a solvent is another option
that may result
in a significant reduction in the coarse minerals content of bitumen product
before
upgrading. When a coker is used for bitumen upgrading to synthetic crude oil,
low solids
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Mr Jan Kruyer P.Eng. Thorsby, fllberta
content bitumen may possibly be upgraded without the need for expensive
dilution
centrifuging since coke normally is a byproduct that is discarded. This coke
would
contain the solids of the bitumen coker feed. Alternately the bitumen product
may be
mixed with a straight chain hydrocarbon liquid and allowed to settle in a
vessel to
produce diluted bitumen product containing ultrafines and water effluent
containing
mostly coarser minerals. The bitumen product may be upgraded thereafter to a
useful
hydrocarbon product after the straight chain hydrocarbon has been removed with
a still.
Water washing of bitumen product with fresh water not only removes hydrophilic
solids but also removes chlorides and other water soluble contaminants or
salts from the
product, resulting in a bitumen product that is less corrosive of refinery
equipment during
upgrading. Water from such a product washing step, which water may contain
small
amounts of bitumen, hydrophilic solids, salts and other impurities, may be
used thereafter
as part of the process water for the production of more oil sand slurry. It
may eventually
end up as interstitual water captured between tailings sand grains. As shown
in Example
6, the oleophilic sieve process was found to be very tolerant of process water
minerals
content, and the "dry tailings" of separation contained about 22% water
between the
sand grains.
EXAMPLE 5
Fluid tailings (sludge) from Suncor tailings pond 2 were processed in our
Edmonton pilot plant with the following results in metric tons at a rate that
varied from 1
to 2 metric tons per hour. The plant never broke down during more than a year
of test
work and only one operator was required to observe and manage the test
programs that
separated close to 1000 metric tonnes of sludge.
Total Bitumen Minerals Water
Feedstock 120.08 7.29 27.95 84.84
Product 11.80 5.86 1.75 3.19
Effluent 107.94 1.21 25.92 80.81
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M. Jan Kruyer, P.Eng. Thorsby, Alberta
Based on these data, bitumen recovery from sludge was 100(5.86/7.29)=80% for
sludge
containing 100(7.29/120.08)= 6.1% bitumen. The separation was carried out at
about 10
degrees centigrade and no dilution water was used to thin the sludge. The
bitumen
product was washed with water to remove some of its hydrophilic solids from
the
bitumen product by mixing it with equal portions of fresh water, followed by
oleophilic
sieve separation of the water and product mixture. A significant amount of
mineral
matter was removed from the product in this very preliminary test with bitumen
product
of sludge. The results in weight percent were:
Bitumen Mineral Water
Dirty product 58.1 % 14.9% 27.0%
Cleaned product 60.8% 10.4% 28.8%
Convential bitumen product from froth flotation of mined oil sand slurry
averages 10%
solids, 30% water and 60% water. The above data shows that washed bitumen
product
from oleophilic sieving of tailings pond sludge has the same water and solids
content as
conventional froth flotation product. While the above results were from
washing bitumen
product from sludge after removal from the oleophilic sieve, similar or better
bitumen
products may result when processing oil sand slurries when the adhering
bitumen is
washed with a fine spray of water while it is still on the sieve surfaces
before removal.
Thus, example 5 shows the bitumen recovery results obtained from oleophilic
sieve processing of a large amount of conventional fluid tailings from a
commercial
tailings pond and the quality of bitumen product achieved by sieving. Dilution
water or
heating was not required in the oleophilic sieve pilot plant. The companion
Suncor pilot
sludge plant had about 10 times the processing capacity and employed froth
flotation of
tailings pond sludge to recover bitumen. It did not achieve acceptable bitumen
recovery
nor acceptable bitumen product quality and was abandoned, in spite of using
elevated
temperatures and significant amounts of fresh water to dilute the sludge.
In example 5, the feedstock residence time for oleophilic sieving of sludge
was
between 3 and 4 minutes while, in comparison, the large froth flotation pilot
plant
operated at a residence time of between 30 and 60 minutes.
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Mr Jan Kruyer P.Eng. Thorsby, Alberta
EXAMPLE 6
The results of oleophilic sieve processing of a low grade oil sand are shown
in the
following example in kilograms;
Kilograms Total Bitumen Minerals Water
Feedstock 1929 175 1654 100
Product 363 167 79 117
Fresh water 508
Recirculating water 391 1 85 305
Oversize reject 28 1 24 3
Tailings 2007 2 1553 452
Total in was 2828kg Total out was 2796kg Sampling of the streams for
analyses and water evaporation accounted for about 32 to 36 kg.
Based on these data of processing oil sand ore containing 9.1 % bitumen, the
bitumen recovery was 95.4% resulting in a bitumen product containing 46.2%
bitumen,
21.7% solids and 32.1 % water. Washing of this product with fresh water was
not done
but would have reduced the minerals content of the product. It is noteworthy
from these
data that recycle water containing 22% mineral solids did not interfere with
the 95%
efficient oleophilic sieving process. 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. Recycle water composition here
reported was the
average composition during the test run.
The run lasted 7 hours, which gave the research staff an opportunity to
evaluate a
change in composition of the recycle water from beginning to end. Runs longer
that 7
hours in duration might have resulted in some changes in the solids contents
of the
recycle water. However, this depends on how much of the solids content of the
recycling
water transfers to the voids of the tailings sand during steady state
operation. This
transfer of solids from the recycle water to the tailings sand voids will
likely vary for
various grades of oil sand feedstock tailings. Using recycle water in this
manner saves on
energy requirements since the water was recycled before it cooled.
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Mr Jan Kruyer, P. Eng. Thorsby, 41berla
Water washing of the product would have reduced the minerals content of the
bitumen product but also would have reduced its sodium chloride (or other
salt) content.
Water effluent from the washing operation could then have been used as process
water
for oil sand slurry preparation and separation, resulting in the deposition of
some of the
salt interstitually between the sand grains of the "dry tailings" that
contained about 22%
water. However, these possibilities were not considered when the test run of
example 6
was carried out, but became apparent after completion of the test work..
EXAMPLE 7
Two metric tons of mined oil sands per hour, at ambient temperature of 10
degrees centigrade, containing by weight 11.2% bitumen, 85.2% mineral and 3.6%
water
are crushed and re-crushed to pass a 0.5 inch by 0.5 inch mesh grizzly. Three
and a half
metric tons of tons of water per hour at 40 degrees centigrade are mixed with
the crushed
oil sand in a revolving tumbler provided to digest the oil sand in water. A
circular mesh
screen at the exit of the tumbler allows the passage of undersize digested
mixture but
prevents the passage of oversize larger than 2 mm. The mesh screen is large
enough to
hold three hours of oversize accumulation. About 400 grams per hour of sodium
hydroxide dissolved in water are added to the mixture per hour to maintain a
constant pH
of 8.3 and facilitate digestion of the oil sand to a slurry. The screened
slurry flows into
an agglomerator with apertured cylindrical wall that is partly fille with iron
balls 20 mm
in average diameter. An oleophilic sieve surrounds the bottom of the
agglomerator
similar to the agglomerators described in copending patent application
2,690,951 filed
February 23, 2010. The surface speed of the oleophilic sieve is 0.2 meters per
second. A
stirred mixture of water and calcium sulphate (gypsum) are added to the slurry
entering
the agglomerator, representing an addition of approximately 200 grams of
gypsum per
hour. In the agglomerator, bitumen particles of the slurry agglomerate to form
bitumen
phase and ultrafines are captured in this bitumen phase, and then the
agglomerated slurry
flows through the drum apertures to the oleophilic sieve for separation.
Bitumen of the
slurry adheres to the sieve along the apertured drum wall and is removed from
the sieve
in a bitumen removal zone away from the drum surface. Tailings of slurry
separation
pass through the sieve apertures in the separating zone and are discarded.
Samples of
CA 02696181 2010-03-12
Mr Jan Kruyer, P. Eng. Thorsby, 41beria
these tailings are collected every 20 minutes after the pilot plant has
operated for at least
five hours to reach steady state. The samples are placed in a centrifuge and
are spun for
twenty minutes at 1000 relative centrifugal force (i.e. 1000 times the force,
of gravity).
After centrifuging, the supernatent liquid of each sample is evaluated. In all
cases the
supernatent water is clear, and only a very low concentration of colloidal
particles are
visible by standard laboratory colloid detecting (light scattering) methods.
As a check, the
gelatine conditions of the supernatent water is determined by NMR
measurements.
EXAMPLE 8
1000 kg of conventional middlings from a large froth flotation pilot plant
processing low grade oil sand ore (8.6 wt% bitumen) were processed by a small
oleophilic sieve pilot plant. The middlings feedstock contained by weight 5.8%
bitumen,
45.2% solids and 49.0% water, and yielded a product containing 58.6 % bitumen,
14.7%
solids and 26.7% water. Solid tailings were removed by auger, containing 0.5%
bitumen,
74.1 % solids and 25.4% water. Fluid tailings were removed by hydrocyclone
underflow,
containing 1.1% bitumen, 50.6% solids and 48.3% water. Hydrocyclone overflow
was
recycled to provide suitable feedstock flow. During these tests, the average
bitumen
recovery from middlings was 79 percent.
The above examples have provided some indication of the merits of the
Oleophilic Sieve for processing a range of feedstocks. The oleophilic sieve
represents
new technology and, as the jet engine has replaced the propellor for moving
airplanes, the
Oleophilic Sieve will replace froth flotation in due time to process oil
sands. The many
new patent applications referred to above have been prepared to make that
possible.
SUMMARY OF THE INVENTION
The present invention is specifically drawn to optimizing the recovery of
valuable
bitumen product from a slurry of mined oil sand and water, and the removal of
ultrafines
from such a slurry. In the present invention, the ultrafines are captured into
the bitumen
phase of the slurry as this slurry is separated by a process that does not use
froth flotation
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Mr Jan Kruyer P.Eng. Thorsby, fllberta
in settling vessels. In stead, it uses bitumen agglomeration of the slurry
followed by
collection of bitumen phase by an oleophilic sieve whilst the resulting
debituminized
slurry passes through the sieve apertures to disposal in the form of tailings.
The
oleophilic sieve can be a mesh screen, but preferably is a rugged revolving
endless belt
comprising adjacent wraps of endless rope or cable. During sieving, bitumen
adheres to
the wraps and tailings or effluent pass through the spaces between adjacent
wraps in
separation zones. Since the wraps revolve, each separation zone is followed by
a bitumen
removal zone, where bitumen is removed from the wraps to be collected as the
bitumen
product of separation.
Oil sand fluid tailings contain a wide range of particulates including several
types
of clay but only some of these particulates are bad actors that cause
thixotropic gels to
form in tailings ponds and prevent fluid tailings compaction and dewatering.
These bad
actors are extremely small in physical size and comprise only a small
percentage of the
fine minerals found in oil sand ore. However these bad actors have extremely
large unit
surface areas and are very effective in forming colloidal thixotropic gels.
Small bitumen
particulates, bi-wetted particles and nano size clay particles in fluid
tailings all do their
part to block the release of water from fluid tailings after these have
settled and gelled in
a tailings pond. It is the objective of the present invention to directly
remove from the
slurry most of these undesirable particles by capturing these into the bitumen
phase
before separation; and to minimize the amount of undesirable particles in the
tailings of
separation; those particles that tend to reduce or stop the dewatering of
tailings. A general
flow diagram of the sequence of steps of the process of the instant invention
are
illustrated in Figure. 1 and is described in broad terms as follows:
Step 1: Mining of an oil sand ore and crushing of the mined ore to reduce the
size of
rocks and lumps to facilitate transport of the subsequent slurry, prepared in
step 2,
through a pipe.
Step 2: Preparation of a suitable aqueous slurry from the mined oil sand ore
by
thoroughly mixing water with the ore. In this preparation step bitumen is
disengaged
from the sand and fine mineral grains of the ore to prepare aqueous slurry.
This
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Mr Jan Kruyer, DEng. Thorsby, 4lberta
slurry preparation step uses natural detergents that are present in oil sand
ore for the
disengagement. Small amounts of sodium hydroxide, carbonate, bicarbonate,
silicate
or similar single valent cation reagents are added to the slurry as needed to
augment
dispersion of slurry particulates by single cation reagents already present in
the oil
sand ore or in the recycle water reused from a tailings pond. These cations
are
present or are added to disperse the slurry and react with oil sand ore to
produce more
detergents, which help in the desired digestion or disengagement of bitumen
from the
oil sand matrix. Recycle pond water, when used in part to prepare this slurry,
generally contain sodium based detergents and sodium chemicals that may help
in the
disengagement process and release bitumen from the oil sand matrix. However
oil
sand ore and process recycle water may also contain monovalent salts that
interfere
with the dispersion of particulates in an oil sand slurry. An example of such
a
monovalent salt is sodium chloride, which tends to acts as an electrolyte and
may
interfere with the dispersion process. In that case, additional mineral
dispersion
monovalent process aid may be required for effective dispersion of the slurry
particulates. In the dispersion process, the process aids attach electrical
charges to the
particulates so that these particulates repel each other. However, when sodium
chloride, calcium chloride, potassium chloride, calcium hydroxide, calcium
sulphate
or other salts that reduce particle dispersion are present in the oil sand ore
or in the
recycle water, these may tend to neutralize or remove the electrical charges
from the
slurry particulates, requiring a larger dosage of minerals dispersing process
aid.
One major difference, that sets this slurry preparation step apart from the
conventional slurry preparation step used in froth flotation bitumen
extraction
processes, is that adhesion of bitumen particles to air bubbles is not the
objective of
step 2. Thus, it is to be understood that undesirable salts are not added to
the slurry
during step 2 but unfortunately may be present in the oil sand ore and/or in
the
recycle water, requiring higher dosages of mineral dispersing reagents.
Step 3: Removal of coarse particulate matter from the slurry, for example, by
settling
vessels or by a hydrocyclone optimized for that purpose. The hydrocyclone
disclosed
in application 2,638,550 may be one type of hydrocyclone used for this
purpose. It
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Mr Jan Kruyer P.Eng. Thorsby, fllberta
uses a coiled pipe ahead of the hydrocyclone body and removes oversize through
the
underflow and encourages bitumen and fines dispersed in water to leave through
the
hydrocyclone overflow. In that case, small amounts of gas or air may be
injected into
the hydrocyclone helical confined path (coiled pipe) to encourage finely
dispersed
bitumen to report to the hydrocyclone overflow instead of to the underflow, as
described in application 2,638,550.
Step 4: The transport, or transfer of, suspension from which oversize has been
removed, to a bitumen agglomerator to increase the average bitumen particle
size.
Oleophilic mineral particulates and bi-wetted minerals report to the bitumen
phase
before or during agglomeration described in step 5.
Step 5: The addition of just enough multivalent cations to the slurry (before
or during
agglomeration) to replace all or most of the single valent (sodium hydoxide or
similar
reagent) cations from the surfaces of nano size ultrafine mineral particles
with
multivalent cations. Multivalent cation may be added to the slurry before
coarse
minerals are removed, to the suspension from which oversize has been removed
or to
the contents of the agglomerator. The amount of multivalent cation addition is
carefully controlled. It must be adequate to cause replacement of single
valent
cations by multivalent cations on the surfaces of gel forming colloidal
ultrafines but
not enough to cause major cation replacement on those particulates that do not
normaly produce gel forming colloids. The amount of multivalent cation
required
will depend to a large degree on the type of oil sand processed, on the type
and
amount of process water used, on the amount and chemical and colloidal content
of
process recycle water used, and on the process conditions. However, the
effectiveness of cation replacement on the surfaces of ultrafines may be
measured and
optimized by observing the tailings efffluent of separation by the methods of
the
present invention. Tailings samples of the oleophilic sieve separation process
may be
evaluated for colloid content of the supernatent liquid after settling or
centrifuging.
The clarity of this supernatent liquid, at the selected separation process
conditions, is
a measure of the effectiveness of this invention and provides a guide as to
the
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Mr Jan Kruyer, P.Eng. Thorsby, 41berta
optimum amount of multivalent cation addition required for a particular oil
sand
slurry being processed.
Step 6: Transport of mixture after agglomeration to one or more separation
zones of
a revolving oleophilic sieve for separation into bitumen phase and tailings
effluent.
The preferred sieve comprises multiple wraps of cable belt, where agglomerated
bitumen phase of the suspension adheres to the wraps and debituminized aqueous
phase tailings of the suspension passes between the wraps to disposal or
further
processing.
Step 7: Adhering bitumen phase is removed from the sieve surfaces or cable
wraps in
one or more bitumen removal zones. Before bitumen removal, wash water may be
sprayed on bitumen adhering to the sieve surfaces to remove some of the
superficially
adhering minerals
Step 8: Bitumen phase removed from the sieve surfaces or cable wraps may be
mixed
with water and reseparated to remove solids or may be processed further. Water
effluent from washing bitumen may be used as part of the process water for
preparing
more oil sand slurry
Step 9: Transportation of debituminized tailings to a dewatering facility
which may
include mechanical dewatering, or may include settling, compaction and
dewatering
in a short duration tailings pond.
Step 10. Reclamation of the dewatered oil sand tailings to an acceptable and
tractable
landscape that may then be planted with flora such as trees and grasses.
Mesh belts may be used as the oleophilic sieve in a pilot plant instead of
cable wrap belts
but mesh belts normally are not rugged nor suitably long lasting to be used
for a
commercial plant. Mesh belts are used in these descriptions to identify that
mesh belts are
part of the claims of this invention.
CA 02696181 2010-03-12
Mr Jan ,-rye,-, P.Eng. Thorsby, 4lberta
The generally ten steps of this invented process require a much shorter total
processing time than is currently required in the commercial bitumen froth
flotation oil
sand extraction process. An important benefit of this instant invention is
that most of the
conventional oil sand gel forming ultrafines are captured in the bitumen phase
of
oleophilic sieving of oil sand slurry and only a small amount of such fines
report to the
tailings of separation. It is anticipated that reducing the amount of
ultrafines reporting to
tailings of separation will beneficially reduce the time required before
tailings can be
remediated into a suitable reclaimed oil sands landscape. However, long
duration test
programs of several years are needed to measure the actual benefits. Waiting a
few years
for those confirming numerical results before applying for a patent was not an
acceptable
option.
RELATED ART
The present invention uses calcium oxide, calcium hydroxide, calcium sulphate
or
other multi-valent salts or hydroxides as an additive during oil sand slurry
separation to
capture ultrafine mineral particles by bitumen phase before bitumen is
separated from the
slurry by an oleophilic sieve.
Canadian patent application 2,581,586 of Baki Ozum filed on 15th September
2007 entitled: Extraction of Bitumen from oil Sands Using Lime, uses lime as
the primary
process aid to extract bitumen from oil sand ore. It contains only two claims
and it deals
strictly with froth flotation and enhancing the efficiency of bitumen recovery
from oil
sands ore by adding lime to oil sands ore-water slurry. Instead of monvalent
cation
addition, such as from sodium hydroxide, Ozum uses lime as the primary process
aid, to
enhance the attachment of bitumen droplets to air bubbles in a bitumen
extraction PSV
type bitumen froth flotation process. In his patent Mr. Ozum uses froth
flotation and does
not contemplate any other type of bitumen extraction process. He teaches the
use of lime
to remove a layer of clay particles from the surfaces of bitumen droplets so
that these
bitumen droplets more readily can attach themselves to air bubbles in a
quiescent vessel,
and rise more efficiently to the top of a froth flotation vessel. In contrast
the instant
invention has as an objective the actual capture of ultrafines by bitumen
phase
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Mr Jan Kruyer, P.Eng. Thorsby, 41berta
agglomeration. This is opposite to the objectives of Mr. Ozum, who uses
calcium ions to
enhance the capture of bitumen by air bubbles, and who does not use bitumen
agglomeration in an agglomerator. Unlike the froth flotation in a PSV method
of Ozum
the present invention uses a completely different method for recovering
bitumen product
from oil sand slurry.
Canadian patent 2,1354,962 of Robert Schutte (a 30 year research employee of
Syncrude Canada Ltd) discloses the addition of sodium silicate to recycle
water from a
tailings pond to keep the ultrafine mineral particles that are present in this
recycle water
from forming colloidal gel structures. In addition to fresh water, tailings
pond water is
used in his invention as recycle water for slurry preparation to separate oil
sand ore by
bitumen froth flotation. This recycle water normally contains colloidal gel
forming
ultrafines. He teaches that ultrafines will not flocculate and form gels as
long as recycle
water is mixed with sodium silicate, and is recycled from the top of a pond
within six
weeks. He further teaches that the ultrafines will restart gel formation in a
tailings pond if
the tailings water is left undisturbed for more than 6 weeks. His method
requires the use
of a very small tailings pond from which process water is recycled
continuously and
which produces solid wet sand tailings that capture ultrafines in the voids
between the
sand grains. In a subsequent report Dr. Schutte states that his employer has
chosen not to
use his process in view of the great expense involved in using a commercially
unproven
process that would require a major revision of the tailings ponds and of the
commercial
extraction plant flow diagram. Unlike the process of Schutte, the instant
invention
captures ultrafines in bitumen product instead of in tailings sand and uses
multivalent
cations instead of sodium silicate to achieve the desired objective. Schutte's
objective for
using sodium silicate is not directed specifically to the dispersion of all
mineral particles
in the preparation of an oil sand slurry but rather is directed to keeping
ultrafiness
suspended in tailings recycle water, so that ultrafines do not have an
opportunity to form
thixotropic gels in tailings ponds.
ADVANTAGES
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Mr Jan Kruyer P.Eng. Thorsby, 41berta
Less energy is required for separation by an oleophilic sieve as compared with
separation by froth flotation. Other advantages are lower water demand,
shorter
residence time, smaller equipment and cleaner bitumen products. In some cases
oleophilic sieve separation equipment may be small enough to allow the
separation plant
to move along with the mine face. This will reduce in a major way the
distances required
to move oil sand, oil sand slurry, and tailings. In addition to commercial
savings that
may result from these transport advantages, major savings also will result
when tailings
compaction and dewatering is speeded up by implementing the present invention
to
reduce the size of tailings ponds and the associated expensive dykes to
contain oil sand
tailings. It will be well worth the effort to conduct economic feasibility
studies to
compare the economic advantages of oleophilic sieving over froth flotation by
an
organization not specifically committed to froth flotation.
AMOUNT OF ULTRAFINES IN A SLURRY
A large number of oil sand research scientific papers, detail that ultrafine
mineral
particles do not represent a large fraction of oil sand ore and yet cause the
formation of
thixatropic gels in oil sand tailings ponds, which gels prevent the natural
compaction and
dewatering of tailings pond sludge (fluid tailings) to less than 60 weight
percent water.
The minerals of average oil sand ore normally contain clay in small amounts,
and only a
small fraction of this clay takes the form of nano size ultrafines. The
present invention
captures ultrafines in the bitumen phase and thereby limits the amount of
ultrafines
entering the tailings ponds. With very low ultrafines concentration in the
fluid tailings of
a pond, no thixotropic gells are formed. This absence of ultrafines allows the
fluid
tailings of a tailings pond to dewater relatively fast and makes these
tailings suitable for
environmentally acceptable reclamation.
BRIEF DESCRIPTION OF THE FIGURE
Fig. 1 is a flow diagram of the present invention
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Mr Jan Kruyer, P.Eng. Thorsby, 41berla
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
made to a
given terminology in several definitions, these references should be
considered to
augment or support each other or shed additional light.
"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 sieve. Agglomeration may be accomplished in a
revolving
drum that contains oleophilic surfaces. For example, the drum wall may be
oleophilic, or
oleophilic baffles or oleophilic tower packings inside the drum may provide
surfaces for
capturing dispersed bitumen phase from a slurry and increase the size of the
bitumen
particles by adhesion before these are sloughed of due to drum rotation.
Alternately the
drum may contain a bed of tumbling oleophilic balls that capture dispersed
bitumen
particles from the slury and release enlarged bitumen phase particles
thereafter. Yet
another method of agglomeration uses a rotating mixer in vessel filled with
slurry. In this
case, bitumen particles of the slurry, revolving in the vessel, come in
contact with other
bitumen particles of the slurry and adhere to each other to form enlarged
bitumen phase
particles.
"apertured agglomeration drum" refers to a drum with an apertured cylindrical
wall containing oleophilic surfaces that 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.
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Afl- Jan Kruyer, P.Eng. Thorsby, 4/berta
"aligned" and "lined up with" as used in these specifications have a slightly
different meaning. For example, apertures in a commercial punched sheet of
steel may
be aligned, that means, the centres of these apertures may be joined by a
straight line.
Oleophilic cable wraps may be aligned, that means that cable wraps are
parallel and in
spaced relationship to each other. On the other hand, cable wraps may be lined
up with
aligned apertures on an apertured drum wall. That means each cable wrap is in
line with
a row of apertures around a cylindrical drum wall.
"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 bitumen droplets that have been
agglomerated
into enlarged bitumen.
"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 cable wrapped around two or
more rollers or drums where the spaces between sequential cable wraps form
apertures
through which aqueous phase can pass, giving up some or most of its bitumen
content to
the wraps as bitumen passes and contacts the wraps. Alternately it refers to
adjacent
single endless cables in contact with supporting rollers or drums. Single
endless cables
may be placed next to each other to form a sieve whereby aqueous mixture can
pass
between the single cable wraps and bitumen may be captured by the wraps.
"critical speed" is the speed of rotation of a drum, containing a bed of
balls, in
which at least some balls of a bed inside the drum remain in contact with the
drum wall at
all times due to centripetal force and due to adhesion of balls to the drum
wall by bitumen
at process temperature. For a conical drum, critical speed computation of the
drum is
based on the largest internal diameter of the conical drum. A bitumen
agglomerator drum
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Mr Jan f(ruyer P.Eng. Thorsby, 4/berta
normally is operated well below its critical speed to allow for mixing of
balls, aqueous
phase and bitumen in a bed of balls for the efficient capture of dispersed
bitumen
particles on ball surfaces from bitumen containing aqueous mixtures and to
allow for
kneading of accumulating bitumen phase by the bed of balls. Critical speed may
be
expressed in terms of drum RPM or in terms of surface speed at a particular
location on
the internal drum wall.
"cylindrical" as used herein indicates a generally elongated shape having a
circular cross-section of approximately constant diameter.
"conical" as used herein indicates a generally elongated shape having a
circular
cross-section with progressively increasing or decreasing diameter along its
length.
"debituminized suspension" is a suspension from which bitumen has been at
least
partly removed
"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 oleophilic sieve. 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.
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A r. Jan Kruyer, P.Eng. Thorsby, f11berta
"long splice" refers to a splice used in the marine and in the elevator
industry to
join the ends of ropes, wire ropes or cables to increase the available length
of such ropes
or cables or to make them endless while providing good strength in the rope or
cable at
the splice. The diameter of the rope or cable at a long splice normally is not
much larger
than the average diameter of the rope or cable itself.
"multiple wrap endless cable" as used in reference to separations processing
refers to a revolvable endless cable that is wrapped around two or more drums
and/or
rollers a multitude of times to form an endless belt having spaced cables.
Proper
movement of the endless belt can be facilitated by at least two guide rollers
or guides that
prevent the 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 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 recovery 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
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Mr Jan Kruyer, P.Eng. Thorsby, Alberta
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 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 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 such 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 a
surface is
not oleophilic as defined under the terms of the present specifications.
Similarly, a rope
(wire or plastic) covered with a thin layer of hot bitumen will not be very
oleophilic as
defined herein until the thin layer of bitumen has cooled down sufficiently 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. The optimum processing temperature is 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.
Normally the processing temperature is below 40 degrees centigrade. When the
temperature is too high, the viscosity of pure bitumen is too low and the
bitumen will not
adhere well to the sieve surfaces. Therefore, process efficiency is reduced
when the
mixture temperature is too high.
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Mr Jan Kruyer, P.Eng. Thorsby, 4/berta
"oleophilic sieve" as used in these specifications refers to an apertured
endless
revolvable belt made from oleophilic mesh material, from oleophilic multiple
rope wraps
or from oleophilic multiple cable wraps. Apertures in an oleophilic sieve are
the mesh
openings in a mesh belt or 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
wraps to separate bitumen from an aqueous mixture, water and suspended
hydrophilic
solids pass through slits between sequential wraps, whilst bitumen phase is
captured by
wraps in a separation zone. The captured bitumen phase is subsequently removed
from
the oleophilic belt (or wrap) surfaces in a bitumen removal zone to become the
bitumen
product of separation.
"oversize" refers to any rigid solids that approach in size the apertures of
the mesh
belt or that approach the linear distance between adjacent cable wrap
surfaces, and
preferably refers to any solids that are larger than 10% of the linear
distance between
adjacent cable wrap surfaces or of the mesh openings. Very large oversize
particles have
difficulty passing mixture dispenser apertures and also have difficulty
passing between
adjacent cable wraps, or through apertures. In addition, sand particles from
oil sand ore
tend to be very abrasive and may cause damage to mesh belts, cable wraps and
distributor
outlets. These smaller particles preferably are also removed as part of the
oversize before
the mixture is allowed to pass through oleophilic sieve apertures. The smaller
particles
may be as small as sand. Therefore, any mixture of large mineral rigid
particles and sand
size particles may be called oversize as defined in these specifications. A
hydrocyclone is
one device that may be used to remove oversize from a mixture before it is
allowed to
pass through an 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, and bitumen removal generally
refers to the
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Mr Jan Kruyer, P.Eng. Thorsby, Alberta
removal of adhering bitumen from the oleophilic sieve surfaces. Bitumen is
recovered
from a mixture in a separation zone through the adherence of bitumen to cable
wraps
upon contact. Bitumen is stripped or removed from cable wraps 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 continuously in a bitumen
recovery zone in order for a bitumen recovery apparatus to continue working
properly to
capture bitumen from an aqueous mixture on cable wraps in a separation zone.
The same
applies to an oleophilic mesh belt.
"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 cable wraps. However
it is
highly undesirable for oversize rigid particles to be retained on cable wraps
or on mesh
belts 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.
"shell" refers to the outside wall of a cylindrical or conical vessel section.
It may
be the apertured wall of a cylindrical agglomerator or it may be the un-
apertured wall of a
conical section of an agglomerator that is attached to an apertured
cylindrical shell.
"sieve" refers to screen, and is used interchangeably with screen unless
stated
otherwise. Sieve refers to a mesh belt or 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
CA 02696181 2010-03-12
Mr Jan Kruyer P.Eng. Thorsby, Alberta
wrap when sequential cable wraps are of different lengths, unless the cable
wraps can
stretch. 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.
"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 containing cations and anions.
The terms "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 a 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
monovalent 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. As another example, when sufficient multivalent process
aid is
added to the slurry after it has been prepared, the amount of multivalent
process aid
added is sufficient to cause most of the mineral ultrafines of the slurry to
adhere to
bitumen but not enough to cause an undesirable amount of larger mineral
particles, that
were hydrophilic in the original slurry, to adhere to bitumen.
"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
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Mr Jan Kruyer, P. Eng. Thorsby, Alberta
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 surface of an agglomerator
cylindrical wall, the surface of a conical agglomerator wall at a specific
location on the
conical wall or is the speed of movement of the surface of a cable screen.
"Tailings effluent" as used herein is debituminized oil sand slurry that has
passed
through the apertures of an oleophilic sieve. It may refer to tailings soon
after these have
passed through the apertures but may also refer to tailings of oleophilic
sieving 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. These specifically
are thixotropic
gel forming colloidal particles, but may also include 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 the 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 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
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Mr Jan Kruyer, P. Eng. Thorsby, Alberta
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-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 headings in the present disclosure are provided for convenience only.
DETAILED DESCRIPTION OF THE FIGURE
Process steps of the present invention are detailed in a flow diagram with
boxes identified
by the letters A to J.
A) Oil sand ore is mined and is crushed to allow processing of the oil sand
ore into
an aqueous slurry with water. For example mined oil sand may be crushed before
water
is added to allow the oil sand to flow in water in a pipeline. Without
crushing, the ore
could contain rocks and lumps that are too large for entry into a pipeline or
are large
enough to cause major pipe wall erosion. When a tumbler is used to prepare the
slurry,
very large rocks could do damage to the equipment when tumbling in a revolving
tumbler.
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Mr Jan Kruyer, P. Eng. Thorsby, ,4lberta
B) Slurry preparation may be done in a tumbler or in a slurry pipeline
transporting
the oil sand from the mine site to a bitumen extraction plant. When using a
pipeline,
turbulence in the pipe causes the oil sand to become a slurry after suitable
additions of
water and monovalent cation process aid. Alternately, when a shorter distance
between
the mine face and the bitumen extraction plant is desired, a serpentine pipe
may be used
to prepare the slurry. This serpentine pipe is disclosed in Canadian patent
application
2,638,551 and uses extreme turbulence and mixing of oil sand ore with water to
achieve
rapid slurry formation. Some oil sand ores contain significant concentrations
of natural
detergents, and in that case, less monovalent process aid is required. This is
especially so
when the oil sand ore is of high grade and/or is very low in calcium or
magnesium salt
content. When recycle water from a tailings pond is used, this water may
contain
detergents and residual monovalent process aid, further reducing the required
amount of
monovalent process aid.
C) Oversize produces problems when separating oil sand slurry by an oleophilic
sieve. The oversize is removed before the slurry is agglomerated and sieved.
Oversize
removal may be done by allowing slurry to be sorted by size and density in a
vessel with
upward flowing water. It may also be done by screening the slurry through a
hydrophilic
screen or preferably it may be done by means by processing the slurry in a
hydrocyclone.
In that case most of the oversize leaves through the hydrocyclone underflow
and most of
the bitumen and undersize leaves through the hydrocyclone overflow. A
hydrocyclone
specifically designed for sorting oil sand slurries for subsequent separation
by an
oleophilic sieve is disclosed in Canadian patent application 2,661,579.
Multivalent cation
process aid may be added before sorting the slurry but it preferably is added
to the slurry
after the oversize has been removed. The amount of multivalent cation added is
carefully
controlled to optimize the subsequent capture of ultrafines of the slurry into
bitumen
phase during agglomeration but to minimize the capture of larger mineral
particles by
bitumen during agglomeration. In some cases the oil sand ore may be high in
calcium or
magnesium salts, which has the effect of reducing the required amount of
multivalent
process aid addition to the slurry. A test procedure may be used to determine
the
optimum amount of multivalent process aid required. In this procedure a sample
of
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Aft- . Jan Kruyer, P.Eng. Thorsby, 41berta
tailings effluent is centrifuged for long enough and at an RPM high enough to
settle most
of the minerals while allowing the colloidal particles to remain in
suspension. Routine
laboratory procedures may be established to achieve this objective, after
which the
concentration of colloidal particles in the supernatent water may be
determined. The
optimum amount of multivalent cation addition may then be determined after a
significant drop in cloudiness of the supernatent water is observed by
standard laboratory
methods. Increasing the amount of multivalent cation addition beyond that
point would
be counter productive, since it would leave too much multivalent cation
content in the
effluent and could increase the capture of coarser mineral particles in
bitumen product.
Leaving too much multivalent cation in the slurry effluent is
counterproductive since
multivalent cations tend to interfere with slurry production by using recycle
water from
settled tailings effluent. It would undesirably increase monovalent cation
process aid
demand during slurry production. Under ideal conditions the multivalent
cations replace
or release all the monovalent cations from the surfaces of the ultrafines
only, and these
released monovalent cations become part of the tailings effluent. When the
supernatent
water from settled and compacted tailings effluent is reused for subsequent
slurry
preparation and dispersion, these released cation dispersants serve as an aid
to disperse
the oil sand slurry.
D) After oversize removal the slurry is agglomerated to increase the size of
the
individual bitumen particles of the slurry, agglomerate them into bitumen
phase and to
cause capture of ultrafines in this bitumen phase. Agglomeration may be done
by means
of a slowly turning mixing paddle or impeller in a tank filled with oil sand
slurry from
which oversize has been removed. Paddle revolutions in the tank allow mixing
of the
slurry, adhesion of bitumen particles to bitumen particles and adhesion of
ultrafines to
bitumen surfaces and capture into bitumen phase. A more effective method is to
tumble
the slurry in a revolving horizontal drum that contains internal oleophilic
walls,
oleophilic baffles or oleophilic tower packings. Another, even more effective
method is
to tumble the slurry in a drum that has an apertured cylindrical wall and
contains a bed of
tumbling oleophilic balls. In this case an oleophilic sieve may cover part of
the apertured
CA 02696181 2010-03-12
Mr Jan Kruyer, P.Eng. Thorsby, fllberta
drum wall to provide a separation zone. These various types of agglomerator
drums are
discribed in detail in patents granted to or pending for the present inventor.
E) After agglomeration the slurry is passed through an oleophilic sieve where,
in one
or more separation zones, bitumen phase is captured by the sieve surfaces and
the
resulting debituminized slurry passes through the sieve apertures to become
tailings
effluent. The captured bitumen is removed in one or more bitumen removal
zones.
F) Bitumen removed from the sieve may be cleaned to remove residual water and
to
remove coarse hydrophilic solids. One effective method is to thoroughly mix
the
bitumen product with water to break up the bitumen phase and re-disperse it in
water.
After that, an oleophilic sieve is used to separate this mixture into bitumen
phase and
water phase. This water phase then contains hydrophilic solids that were part
of the
bitumen phase before clean up. Small amounts of detergents may be used during
bitumen clean up to water wet coarse mineral particles and cause them to
report to the
water phase.
G) After this preliminary bitumen clean up the bitumen may be dilution
centrifuged
to remove coarse solids as done in conventional oil sand plants, or may be
mixed with
straight chain hydrocarbons to separate the hydrocarbon phase from the aqueous
phase by
settling. In most cases the ultrafines remain with or can be made to remain
with the
bitumen hydrocarbon phase and these ultrafines can then be removed as part of
a solids
effluent during bitumen coking or during other types of bitumen processing to
produce
synthetic crude oil.
H) Tailings effluent may be dewatered with thickener types of vessels, with
hydrocyclones, with centrifuges, or simply by allowing the effluent to settle
and compact
in tailings ponds. Tailings effluent settling will result in supernatent clear
water on top of
tailings ponds that can be recycled. Settled and dewatered compacted effluent
may
continue to fill a pond or a mine pit until it is full. The important
difference between the
present invention and the conventional commercial oil sand extraction method
is that the
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CA 02696181 2010-03-12
Ai Jan A-ruyer P.Eng. Thorsby, fllberta
tailings effluent of the present invention are expected to compact much faster
than the
fluid tailings of a conventional mined oil sands plant. This will result in a
major
reduction in fresh water demand for processing oil sands. An increased amount
of
recycle water can thus be used to replace the current demand for fresh water.
J) Compacted tailings may be dredged from tailings ponds to mix with sand and
reagents to form a solid base for use in oil sand site remediation.
Alternately, rope style
centrifuge underflow solids may be used for that purpose. Since the tailings
effluent of
the present invention may settle faster than conventional fluid tailings, the
chemical
demand for tailings remediation may be significantly lower than would be
required for
remediating conventional fluid tailings. Instead of requiring many decades for
conventional fluid tailings compaction, the present process may be expected to
result in
tailings effluent compaction that is about an order of magnitude faster. This
will result in
much faster oil sand site remediation. Determination of the actual speed of
compaction
will require test programs that will last several years.
Of course, it is to be understood that the above-described 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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