Note: Descriptions are shown in the official language in which they were submitted.
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
HELICAL CONDUIT HYDROCYCLONE METHODS
RELATED APPLICATIONS
This application is related to U.S. Patent Application No. 11/940,099,
entitled
"Hydrocyclone and Associated Methods ", filed November 14, 2007, U.S. Patent
Application
No. 12/132,165, entitled "Removal of Bitumen from Slurry Using a Scavenging
gas ", filed
June 3, 2008, Canadian Patent Application No. 2,638,550, entitled
"Hydrocyclone and
Associated Methods", filed August 7, 2008. Note that Canadian patent
application
2,638,550 is a combination of US patent applications 11/940,099 and 12/132,165
but U.S.
application 11/940,099 did not disclose nor make any claims for gas injection.
The present
application is also related to Canadian Patent Application No. 2,644,793
entitled "Endless
Cable System and Associated Methods", filed August 6, 2008, and Canadian
Patent
Application No. 2,647,855 entitled "Design of Endless Cable Multiple Wrap
Bitumen
Extractors ", filed January 15`" 2009, which are each incorporated herein by
reference.
FIELD OF THE INVENTION
The present invention relates to methods for hydraulically sorting and/or
chemically
reacting of flowing aqueous suspensions in a centrifugal force field with the
assistance of
one or more fluids injected into a conduit comprising a helical pipe, tube or
hose in the form
of a coil or spiral ahead of a hydrocyclone open vessel, and the resulting
issuance of an
overflow stream and an underflow stream from the open vessel. Accordingly, the
present
invention involves the fields of process engineering, chemistry, and chemical
engineering.
BACKGROUND OF THE INVENTION
As described in the above referenced patent applications, oil sands, also
known as tar
sands or bituminous sands, may represent up to two-thirds of the world's
petroleum reserve.
In the past, oil sands resources remained relatively untapped. Perhaps the
largest reason for
this was the difficulty of extracting bitumen from the sands. Large deposits
of mineable oil
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Jan Kruyer, Thorsby, Alberta, Canada
sand ore are found in the Fort McMurray region of Alberta, Canada, and
elsewhere. This oil
sand includes sand grains having viscous bitumen trapped between the grains.
The bitumen
can be liberated from the sand grains by suspending the as-mined oil sand
particulates in
water so that the bitumen flecks disengage from the sand grains and disperse
in the aqueous
phase for separation. For the past 50 years, bitumen in McMurray oil sand has
been
commercially recovered using the original Clark Hot Water Extraction process,
along with a
number of improvements. Karl Clark invented his original process at the
University of
Alberta and at the Alberta Research Council around 1930 and improved it for
over 30 years
before it was commercialized. The present inventor knew Karl, and after Dr.
Clark retired,
the inventor used some of the pilot plant space previously occupied by Clark
at the Alberta
Research Council to commence the development his own oil sands process and
overcome
some of the problems of the Clark process.
In general terms, the conventional Clark hot water process, and its commercial
improvements, involve mining oil sands ore at a remote mine site. The mined
ore is then
transported to a bitumen extraction plant by earth haulers or by slurry
pipeline. The ore is
mixed with water and chemicals to condition it to disengage the bitumen
particles from the
sand matrix and form a slurry. This slurry may be conditioned by turbulence in
a pipe during
pipeline transportation between mine site and an extraction plant or it may be
conditioned at
the extraction plant in large tumblers that mix water and/or steam with the
oil sand ore.
Large rocks are removed from the slurry, either by screening the tumbler
product or by
crushing the ore before it enters the pipeline. Normally caustic soda, a
process aid, is added
to the slurry to disperse the mineral particles and to produce detergents by
chemical reaction
with components in the ore, which detergents enhance subsequent bitumen
recovery. The
slurry may be further diluted with water and is then pumped into a primary
separation vessel
(PSV) where it is separated by froth flotation. Bitumen particles adhere to
air bubbles in the
PSV and cause bitumen to float as froth to the top of the vessels to be
skimmed off.
Clark separation produces three components: an aerated bitumen froth which
rises to
the top of the PSV; primary tailings which settle to the bottom of the PSV;
and middlings
which concentrate in the middle of the PSV. The bitumen froth is skimmed off
the top as the
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Jan Kruyer, Thorsby, Alberta, Canada
primary bitumen product. The middlings are pumped from the middle of the PSV
to sub-
aeration flotation cells to recover additional aerated bitumen called
secondary bitumen
product. The primary tailings from the PSV, along with secondary tailings
product from
flotation cells are pumped to the shore of a tailings pond, usually adjacent
to the extraction
plant, for impounding. The tailings sand drops out on the beach and is used to
build dykes
around the pond and the aqueous residue including water, detergents, caustic,
silt, clay, and
residual bitumen flow into the pond to settle for a decade or more, forming
non-compacting
sludge layers near the bottom of the pond. Clarified water, containing
detergents, caustic,
salts, and a small amount of fines eventually rises to the top of the pond for
reuse in the
process.
The primary and secondary bitumen froth are combined and treated to remove air
and
then diluted with diluent, such naptha and centrifuged to produce a bitumen
product suitable
for upgrading. Centrifuging also creates centrifugal tailings that contain
mainly solids, water,
residual bitumen, and naptha, which are disposed of in the same or in another
tailings ponds.
In an alternate process the produced bitumen is extracted with a straight
chain hydrocarbon
liquid to remove water solids and a small amount of asphaltenes by settling,
for example in a
vessel, to produce a bitumen product suitable for upgrading or shipping by
pipeline to a
refinery, and yielding an aqueous tailings product, containing some dispersed
asphalt, sent to
a tailings pond.
The residence time in a Clark extraction plant, comprising the time it takes
from
mining the ore to producing the bitumen froth and disposing of the tailings,
is a function of
the complexity of the commercial plant designed to achieve acceptable bitumen
recovery. It
normally is several hours. Residence time in the PSV alone can be between 30
and 60
minutes to produce primary froth, with additional time taken in the
subaeration cells to
produce secondary froth and in the tailings clean up equipment.
Some major improvements have been made in the Clark process that include
lowering the separation temperature in the tumbler, in the PSV, and in the
flotation cells by
the addition of a small amount of a hydrocarbon diluent to the slurry. This
reduces the
energy costs to a degree but may also require the use of larger tumblers and
the addition of
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Jan Kruyer, Thorsby, Alberta, Canada
more air to enhance bitumen flotation. Another improvement eliminated the use
of bucket
wheel excavators, draglines and conveyor belts to replace these with large
shovels and huge
earth moving trucks. Later improvements replaced some of these trucks and most
of the
costly and high maintenance conveyors with a slurry pipeline. Such a pipeline
transports the
ore as a mixture in water and eliminates the expense of mechanical transport
of the ore from
the mine site to the separation plant. A slurry pipeline also eliminates the
need for
conditioning tumblers. Turbulence in a slurry pipeline about 3 kilometers or
longer normally
achieves the desired conditioning. However, an oil sand slurry pipeline
requires the use of
one or more oil sand ore crushers to prevent pipe blockage by rocks or oil
sand lumps, tree
trunks, etc., and also requires a cyclo-feeder to mix the crushed ore with
water and to aerate
the oil sand as it enters the slurry pipeline. An oil sand slurry pipeline may
also require
compressed air injection into the slurry at one or several points along into
the pipeline.
Other recent improvements in the commercial Clark process include tailings oil
recovery
units to scavenge additional bitumen from the tailings, and naptha recovery
units for
processing the centrifugal tailings before these enter the tailings ponds.
More recent research
is concentrating on efforts to convert the fluid tailings or sludge in the
tailings ponds to
compact these tailings and remediate them. For example,lime, gypsum and/or
flocculants
may be added to the sludge of the tailings ponds after it has settled for one
or more decades,
to compact the fines and release additional water. Most of the improvements
made to the
commercial Clark process have served to make the process more attractive
economically, by
increasing the amount of bitumen recovered, by eliminating expensive
transportation
equipment and by reducing the amount of energy required. These, however, have
also
served to increase the complexity of the commercial oil sands plants without
doing much to
overcome the associated environmental problems of oil sands processing.
One particular problem that has vexed commercial mined oil sands plants is the
problem of fluid fine tailings disposal. Caustic soda serves as a process, aid
to produce
detergents by reacting with components in the oil sand ore and also serves to
disperse the oil
sand fines and thus reduce the viscosity of the slurry suspension in the PSV.
Reducing this
suspension viscosity allows the aerated bitumen droplets to travel to the top
of the separation
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Jan Kruyer, Thorsby, Alberta, Canada
vessels by gravity fast enough to achieve satisfactory bitumen recovery in a
reasonable
amount of time. A graph of the rise velocity of bitumen droplets in a PSV is
supplied in
FIG. 3D to illustrate that bitumen rises about 16 times as fast in a dispersed
suspension as
compared with a suspension that is not dispersed. Electrical charges are
imparted to the oil
sand fines as a result of process aid additions, especially the clay particles
are charged, which
charges repel and disperse these particles and thereby reduce the viscosity of
the dilutedPSV
slurry. When pond water is recycled to the process, this process aid and/or
the produced
detergents, already are present in the water used to prepare the oil sand
slurry or suspension.
When process aid, or recycle water is not used, the diluted slurry of most oil
sands would be
too viscous for effective bitumen recovery in the PSV and in the subaeration
flotation cells.
The graph shows a bitumen rise rate increase of about sixteen, but even three
times the
required residence time would make commercial oil sands extraction too
expensive and
impractical.
While process aid is beneficial for producing detergents and as a viscosity
breaker in
the separation vessels for floating off bitumen, it is environmentally very
detrimental. The
detergents produced from naphthenic acid components in the oil sand slurry are
highly toxic.
Not only are the tailings toxic, but due to the electrical charges and other
components that are
present, the tailings fines take a very long time to settle and compact.
Tailings ponds with a
combined average circumference as large as 20 kilometers are required at each
large mined
oil sands plant to contain these fine fluid tailings. Coarse sand tailings are
used to build huge
and complex dyke structures around these ponds. The very small particles of
the fluid fine
tailings cause the formation of very thick layers of microscopic card house
structures and
jells that compact extremely slowly and take decades or centuries to reach a
solids content
between 30 and 40 weight percent and a water content between 60 and 70
percent. Due to
partial sludge compaction, water rises to the top of the ponds, and this water
contains salts,
process aid, and detergents and is reused in the extraction plants many times
over as recycle
water. In some cases this water may be treated before it is used a recycle
water. For mature
commercial oil sands plants the amount of pond recycle water used in the
extraction may be
five or ten times as much as the amount of fresh water used for the
extraction. The residual
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Jan Kruyer, Thorsby, Alberta, Canada
process aid and detergents in the recycle water tend to significantly reduce
the requirements
for fresh caustic process aid additions to the oil sand slurry in these
plants. However, the
amount of dispersed fluid tailings accumulating in the ajacent oil sands
tailings ponds is
staggering. For example, the current amount of stored fluid tailings (sludge)
could cover a 10
meter wide (two lane) highway 12 meters high (up to the rafters of a four
story building) all
the way across Canada from Victoria to Hallifax. Many millions of dollars per
year have
been and are being spent in an effort to maintain the tailings ponds and to
find effective ways
to dewater these tailings. Several patents have been granted to or are pending
for the present
inventor to solve some of the above described environmental problems and to
reduce the cost
of equipment, chemicals and energy of the current commercial oil sands
extraction plants.
In one application of the art, the Kruyer process uses a revolving apertured
oleophilic
wall to separate aqueous oil sand suspensions. The oil sand suspension flows
to the wall
which allows hydrophilic solids and water to pass through the wall apertures
whilst capturing
bitumen and associated oleophilic solids by adherence to the surfaces of the
revolving
oleophilic wall. Oversize solids are solids that have dimensions approaching
the dimensions
of the wall apertures in at least one dimension, and these are removed before
the mixture is
separated by the apertured wall. Removal of such oversize may be done by the
use of
hydrocyclones independently or in conjunction with screens ahead of the
aperture wall. Such
hydrocyclones are disclosed in copending patent applications and in the
current application.
Other uses of these hydrocyclones are also possible as, for example, in the
froth flotation of
an aqueous suspension of comminuted mineral ore in a centrifugal force field.
Along the revolving apertured oleophilic wall, there are one or more
separation zones
to separate the suspension into an effluent of water with hydrophilic solids
and a product of
bitumen and oleophilic solids. Along the same revolving apertured wall are one
or more
recovery zones where the recovered bitumen and oleophilic solids are removed
from the
wall. This product normally is not an aerated froth but rather a viscous
liquid bitumen. A
prior bitumen-agglomerating step may be required to increase the bitumen
particle size
before the suspension passes to the apertured oleophilic wall for separation..
This Kruyer
process was tested extensively and was successfully implemented in a pilot
plant with high
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Jan Kruyer, Thorsby, Alberta, Canada
grade mined oil sands (12 wt% bitumen), medium grade mined oil sands (10 wt%
bitumen),
low grade oil sands (6 wt% bitumen) and with fluid tailings (sludge) from
commercial oil
sands tailings ponds (down to 2% wt% bitumen), the latter at separation
temperatures as low
as 5 degrees centigrade.
A large number of patents have been granted for the Kruyer process in Canada
and in
the U.S. representing prior art. In this prior art the apertured oleophilic
wall took the form of
a drum only with aperture cylindrical wall or took the form of conventional
mesh belts which
worked fine in the pilot plant for a few weeks but fell apart after extended
use. Conventional
commercial steel conveyor belts were tested and patented also but these did
not perform as
well as the mesh belts. Years later a new type of aperture oleophilic wall was
developed that
made use of one or more revolving endless cables that were wrapped around
rollers and rums
in the form of multiple wraps. The multiple wraps formed the surface of the
apertured
oleophilic wall and the slits or spaces between sequential cable wraps formed
the apertures.
Various still pending patent applications disclose and claim a large variety
of applications
that make use of the multiple cable wrap aperture oleophilic wall. Other
patents are pending
for apparatus or methods to augment or support the use of such an aperture
oleophilic wall
that uses cable wraps, but may also be used in conjunction with the prior art
that uses mesh
belts or conventional commercial steel conveyor belts. The claims of these
copending patents
may be used independently and in many cases may not require the use of an
aperture
oleophilic wall altogether.
Froth flotation in the PSV of the Clark process requires a residence time of
about
to 45 minutes and additional time is taken in the sub-aeration cells to
achieve
acceptable bitumen recovery. Since froth flotation relies on the force of
gravity for its
effectiveness, much shorter residence times can be achieved when a centrifugal
force
25 field is applied to the slurry, especially when this force field is one or
more orders of
magnitude greater than the force of gravity. The present invention takes
advantage of this
greater force field to achieve much faster bitumen froth flotation than is
possible in a
gravity force driven system. The present invention makes use of a hydrocyclone
of
special design which allows the introduction of fluid from jets into a flowing
oil sand
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Jan Kruyer, Thorsby, Alberta, Canada
suspension while the suspension is under the influence of a centrifugal force
field in a
curved conduit, such as a pipe, tube or hose curved into a coil or a spiral,
and before it is
separated into an overflow and an underflow by the open vessel of a
hydrocyclone.
The hydrocyclone design of the present invention includes a curved conduit
ahead
of an open vessel of the hydrocyclone to prepare a flowing suspension for the
subsequent
separation by the open vessel into an overflow and an underflow. Provision is
made for
the injection of one or more fluids under pressure through the conduit wall
into the
flowing suspension. This injected fluid may be a gas, a liquid, a gas
dissolved in a liquid
under high pressure, a chemical dissolved in a liquid, or it may be a finely
dispersed
aqueous suspension, such as milk of lime, finely dispersed gypsum in water or
a fine
suspension of another divalent or trivalent salt in water. Several fluids may
be injected
into the conduit in sequence. This, for example, may be done to allow one
process
operation to precede another process operation or reaction in the suspension
flowing
through the conduit.
When the flowing suspension contains particulate matter of varying sizes or of
varying densities, the coarse or dense particles will tend to gravitate
towards the outer
lane of the conduit and the fine or less dense particles will tend to
gravitate towards the
centre or towards the inner lane of the conduit due to its curvature. This is
similar to the
forces exerted on a passenger in a car that rapidly turns a corner. Jets or
nozzles may be
mounted in the conduit wall to inject fluid into the suspension, or a short
section of the
conduit wall may be made porous and this porous section may be surrounded by a
chamber containing injection fluid under pressure. The injected fluid may
include large
amounts of gas or liquid, causing bitumen and fine particles to dislodge from
the larger
particles and move out of the outside lane towards the middle of the conduit
or to the
inside lane. The injected fluid may cause the adherence of bitumen particles
and/or
hydrophobic particles to gas bubbles and result in the froth flotation of
these particles out
of the outside lane and into the centre or into the inside lane of the curved
conduit under
the influence of the centrifugal force field present in the suspension flowing
in the
conduit. In one objective, an abundance of gas is injected to achieve froth
flotation of
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Jan Kruyer, Thorsby, Alberta, Canada
selected components of the suspension in a centrifugal force field.
Alternately, a much
smaller amount of air or gas may be may be injected through nozzles throug the
conduit
wall, as described in Canadian copending patent application "Hydrocyclone and
Associated Methods ". In this copending application the amount of injected air
or gas was
limited to allow the bulk of the liquid suspension to absorb this air or gas
after it had done
its job of transferring bitumen to the inside lane. In contrast, the objective
of the present
invention is to inject an abundance of gas into the flowing suspension through
the conduit
walls to retain all or most of the bitumen in the suspension in an aerated
form as froth.
This froth then reports, along with water and fines, to the overflow of the
hydrocyclone
open vessel of the present invention. The overflow product mixture may then
sent to a
separation apparatus that uses an aperture oleophilic wall to remove air,
water and some
solids to yield a valuable liquid bitumen product and a discard tailings
product. Unlike
the other pending patent applications of the same inventor, this current
application also
expands the concepts of froth flotation in a centrifugal force field to the
separation of
comminuted ore into valuable minerals and gangue.
Thus, in the present invention, the amount of air or gas used is much larger
than in
the copending art and the overflow of the hydrocyclone contains at least 3%
air by
volume, and in many cases much more. The current application also introduces
the
merits of using more than one hydrocyclone in series to optimize the quality
of froth
produced. The first hydrocyclone may be used to remove coarse solids from the
oil sand
slurry and fluid may be injected through the walls of the conduit to assist in
the transfer
of bitumen and fines from the outside lane to the middle or to the inside
lane. In
subsequent hydrocyclones that follow the first hydrocyclone in series, other
fluids may be
injected through the conduit walls of these hydrocyclones to refine the
desired sorting,
mixing, separation or reaction processes that may take place. For example, the
first
hydrocyclone may be larger in size than the subsequent hydrocyclone or
hydrocyclones.
As a result, the flow velocity through the first hydrocyclone may be lower
than through
the subsequent hydrocyclones. This may result in the removal of very coarse
solids from
the suspension through the first underflow, while allowing a first overflow,
containing
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Jan Kruyer, Thorsby, Alberta, Canada
less coarse solids, to become the feed for the helical conduit of a second but
smaller
hydrocyclone. In most cases the total flow through the first hydrocyclone will
be larger
than the flow through a subsequent hydrocyclone, even if both hydrocyclones
are of the
same size, since part of the flowing suspension is removed by the underflow of
the first
hydrocyclone. Therefore, the relative sizes of several hydrocyclones in series
may be
optimized to control the flow velocity and centrifugal force field in each
hydrocyclone
and thus achieve the objectives of the present invention for each
hydrocyclone.
The methods of the present invention may be used to process oil sand
suspensions, such as oil sand slurries, Clark process or other process
middlings, primary
tailings, secondary tailings, tailings pond sludge, tailings pond sediments or
any other
aqueous stream containing bitumen. However, it may also be used for froth
flotation of
size reduced mineral ores to float off the desired components by adhesion to
gas bubbles
while leaving undesirable components water wetted and in suspension or
settling.
Alternately it may be used to float off undesireable gangue while leaving the
desired
components in aqueous suspension or settling.
The concepts of using a centrifugal force field to remove coarse solids from
an oil
sand slurry is disclosed and claimed in Canadian patent 2,246,841 entitled
"Cycloseparator for removal of coarse solids from conditioned oil sand
slurries" issued to
Maciejewski et.al on 20 November 20`h, 2001 and reissued on Febuary 24`h,
2004. This
patent discloses a very large hydrocyclone that produces an overflow
consisting of
bitumen froth and fines and an underflow of coarse solids in water. This
patent does not
disclose or claim a helical conduit nor any injection of fluid into such a
helical conduit.
The concept of using air injection in a hydrocyclone to cause hydrophobic
particles to
adhere to air bubbles and report to the overflow is disclosed in a Canadian
patent entitled
"Air Sparged Hydrocyclone and Method" issued to Miller on January 4th, 1983.
This
patent discloses a hydrocyclone provided with a gas jacket surrounding part of
the
hydrocyclone body, which jacket has a porous inner wall that allows entry of
finely
dispersed compressed gas into the hydrocyclone vessel to encourage adhesion of
hydrophobic particles to the gas bubbles and cause these to report to the
hydrocyclone
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Jan Kruyer, Thorsby, Alberta, Canada
overflow. Another Canadian patent entitled "Flotation Apparatus for Achieving
Flotation in a Centrifugal Field" issued to Miller on October 1st 1985 uses a
very similar
apparatus to separate minerals from gangue. A hydrocyclone body with separate
inlets
for air and slurry is disclosed in US patent 4,971,685 entitled "Bubble
Injected
Hydrocyclone Flotation Cell" issued to Stanley, et al. on November 20th 1990.
The use
of two hydrocyclone vessels in one housing is disclosed in Canadian patent
entitled
"Hydrocyclone System Including Axial Feed and Tangential Transition Sections"
granted
to Macierewicz et al. on October 9th, 1979. In this patent a stream of coarse
solids is
removed from the system by means of a helical screw flight section before the
remainder
is separated by a conventional hydrocyclone section into an underflow and an
overflow.
In his granted US patent 4,838,434, issued June 13th, 1989, Dr. Miller
provides a
very detailed description of using air sparged hydrocyclone flotation methods
for
separating particles from a particulate suspension. He uses an upright
generally
cylindrical hydrocyclone vessel having a circular cross-section and a
tangential inlet in
the upper portion of the vessel for introducing a suspension in a generally
tangential
fashion; a means for introducing gas into the open vessel, to contact the
suspension; the
gas forming small bubbles, which combine with particles in the particulate
suspension to
form bubble/particle aggregate froth within the vessel. The vessel of the
Miller patent has
a porous cylindrical outside wall that is functionally connected to an air
chamber
surrounding the open vessel, which allows finely dispersed gas to enter the
open vessel
and contact the suspension. Again the Miller patent does not anticipate the
use of a
confined helical conduit ahead of a hydrocyclone vessel for fluid injection in
a flowing
suspension.
Flotation of minerals and the separation of minerals from gangue in
conventional
flotation vessels is described in detail by Somasundaran et. al. in his book
entitled
"Reagents in Mineral Technology" (ISBN 0-8247-7715-8) and Dr. Miller also
provides
an excellent review of minerals flotation in his above referenced patents. I
hereby defer to
both authors as being experts in this field of engineering. Flotation is a
process in which
one or more specific particulate constituents of a slurry or suspension of
finely dispersed
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Jan Kruyer, Thorsby, Alberta, Canada
particles become attached to gas bubbles and form a "bubble and particle
aggregate"
which can be separated from the other constituents of the slurry or
suspension. The
buoyancy of the bubble and particle aggregate, formed by the adhesion of gas
bubbles to
particles in the slurry or suspension, is such that the agregate rises to the
surface of
conventional flotation vessels where it is separated from the remaining
particulate
constituents which remain suspended in the aqueous phase of suspension in the
separation vessel.
Hence, flotation techniques can be applied where conventional gravity
separation
techniques fail and, as a result, flotation has supplanted the older gravity
separation
methods in solving a number of separation problems. Flotation was used
initially to
separate sulphide ores of copper, lead, and zinc from associated gangue
mineral particles
but flotation is now also used for concentrating non-sulphide ores, for
cleaning coal, for
separating salts from their mother liquors, and for recovering elements such
as sulphur
and graphite. It also is used in the reclamation industry to separate plastic
particles from
other materials.
The application of flotation technology to mineral recovery during the past
four
decades has increased at an annular rate of more than 10%. , and present
flotation
installations in Canada, the United States and elsewhere in the world are
capable of
processing well over four million tons of material per day.
Preferred methods for removing the floated material involve the formation of
froths or foams to collect the bubble/particle aggregates. Froths containing
the collected
bubble/particle aggregates can then be removed from the top of the suspension.
This
process is called "froth flotation" and is conducted as a continuous process
in equipment
called flotation cells. Froth flotation is accomplished by the introduction
into these
flotation cells of voluminous quantities of small bubbles, which in the
flotation cells of
the prior art were typically in the range of from about 0.1 to about 2
millimeters in
diameter.
In conventional flotation cells of the prior art, the success of flotation has
depended upon controlling conditions in the particulate suspension so that the
air is
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Jan Kruyer, Thorsby, Alberta, Canada
selectively retained by one or more particle constituents and is rejected by
the other
particle constituents of the suspension. To achieve this selectivity, the
slurry or
particulate suspension is typically treated by the addition of small amounts
of known
chemicals or flotation enhancing reagent fluids which selectively render
hydrophobic one
or more of the constituents in the particulate suspension. Those chemicals
which render
hydrophobic a particulate constituent which is normally hydrophilic, are
commonly
referred to as "activators" or "collectors." Chemicals which increase the
hydrophobicity
of a somewhat hydrophobic particulate constituent are commonly referred to as
"promoters." Treatment with a collector or promoter causes those constituents
rendered
hydrophobic to be repelled by the aqueous environment and attracted to the air
bubbles.
Most importantly, the hydrophobic nature of the surface of these constituents
enhances
attachment of air bubbles to the hydrophobic constituents. Thus, control of
the surface
chemistry of certain particulate constituents by the addition of flotation
enhancing
reagent fluids such as a collectors or promoters allows for selective
formation of bubble
and particle aggregates with respect to those constituents.
Other chemicals or flotation enhancing fluids may be used to help create the
froth
phase for the flotation process. Such reagents or chemicals are commonly
referred to as
"frothers." The most common frothers are short chain alcohols, such as
methylisobutylcarbinol (MIBC), pine oil, and cresylic acid. Important criteria
related to
the choice of an appropriate frother include the solubility and collecting
properties of the
frother, the toughness and texture of the froth, and froth breakage. Hence, an
appropriate
frother normally is chosen to ensure that the froth will be sufficiently
stable to carry the
bubble and particle aggregates for subsequent removal as a flotation product
concentrate.
Dr. Miller refers to the term "concentrate" as a mixture of desired mineral
product and
other entrained minerals which are present in the froth product. He states
that the proper
choice of frother ensures that a froth will allow for the proper drainage of
water and for
the proper removal of misplaced hydrophilic particles from the froth; and that
in practical
flotation tests, the size, number, and stability of the bubbles formed during
flotation can
preferably be optimized at given frother concentrations. Other chemical
solutions added
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Jan Kruyer, Thorsby, Alberta, Canada
to the suspension include "modifiers" which comprise a broad class of organic
or
inorganic compounds that modulate the flotation environment by regulating
solution
chemistry, or by flocculating or dispersing particles in the suspension.
A complete flotation process may be conducted in several steps:
(1) A slurry is prepared containing from about five percent to about forty
percent by
weight solids in water;
(2) The necessary flotation enhancing reagent fluids are added, and sufficient
agitation and time is provided to distribute the reagent on the surface of the
particles to be floated;
(3) The treated slurry is aerated in a flotation cell by agitation in the
presence of a
stream of air or by blowing air in fine streams through the slurry; and
(4) The aerated particles in the froth are withdrawn from the top of the cell
as an
overflow froth product, and the remaining solids and water are discharged from
the bottom of the flotation cell.
A large amount of research and development work has been done in analyzing the
various factors which relate to improving the conditions during flotation in
order to
obtain improved recovery of particles. One particular phenomenon that has been
known
for some time is the poor flotation response of fine particles. This becomes
economically
important when flotation separation methods are used in the processing of
minerals.
Generally, prior art processes using gravity induced flotation, have achieved
flotation for
both metallic and nonmetallic minerals having particle sizes as large as about
1000
microns. In these processes, particles less than 10 to 100 microns in size are
frequently
difficult to recover. One factor in conventional froth flotation, which has
limited the
extent of fine particle recovery is the relatively slow rate at which fine
particles are
separated in the prior art flotation processes which use gravity as the
driving force for
separation. Very small particles take too long to rise to the top of flotation
cells.
Frequently, the mineral industry has thus been forced to discard the smaller,
unrecovered
mineral particles since it is uneconomical to concentrate or recover them. The
economic
losses suffered by the minerals industry due to this inability to recovery
very fine
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Jan Kruyer, Thorsby, Alberta, Canada
minerals by conventional flotation techniques indeed is staggering. For
example, in the
Florida phosphate industry, approximately one-third of the phosphate is
typically lost in
the residual waste slime. Roughly, one-fifth of the world's tungsten and about
one-half of
Bolivian tin is lost due to the inefficiencies of the flotation techniques of
the prior art
currently used in recovery processes for these minerals. The inability of the
prior art of
gravity flotation processes to recover fine particles also is an important
economical and
environmental issue in the coal industry. Flotation processes for separating
ash and
sulphur from coal have been used with greatly increased frequency during
recent years.
However, in these flotation separation processes, significant amounts of very
fine coal
particles are not recovered but leave with the effluent. Not only is this a
waste of a
valuable resource, but disposal of finely dispersed coal-containing aqueous
reject streams
is frequently a serious environmental problem.
A major factor which impacts on the effectiveness of conventional flotation is
that
conventional flotation cells generally require a minimal retention time of at
least two
minutes for successful separation. This relatively long retention time
required for
conventional flotation processes limits the separation plant capacity and
necessitates the
construction of large equipment which result in large floor space demands and
requires
high capital and maintenance expenditures.
Unlike the hydrocyclone disclosed and claimed in the Miller patents, the
present
invention does not use froth flotation hydrocyclones requiring a porous wall
between the
hydrocyclone open vessle and a surrounding gas chamber. Rather, it uses a
conduit
ahead of a hydrocyclone open vessel where the conduit is formed into a coil or
a spiral to
impose a centrifugal force field on the flowing suspension well before it
enters the open
vessel or drum of the hydrocyclone, and fluids, including gas are injected
through the
conduit wall into the flowing suspension. Hence, the present invention does
not use a
porous wall for the open vessel of the hydrocyclone nor an air chamber
surrounding the
open vessel.
The present invention uses a helical conduit ahead of the open vessel of the
hydrocyclone to establish a centrifugal force field in the flowing suspension
well before
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
the suspension enters the open vessel of the hydrocyclone. Consistent with the
above
descriptions of minerals flotation, activators may be used to prepare the
minerals for
flotation, suppressors may be used to prevent other minerals from flotation,
modifiers
may be used to regulate the solution chemistry of the suspension and frothers
may be
used to encourage certain components to adhere to gas bubbles and gas may be
injected
into the suspension to achieve the desired flotation.
Nozzles may be mounted in the conduit ahead of the hydrocyclone open vessel or
porous sections of the conduit may be used to introduce these extra
components, in the
form of fluids under pressure, into the flowing suspension, which suspension
is under the
influence of a centrifugal force field due to its flow through the coil or
spiral. Several
different fluids may be injected in sequence through the wall of the conduit
to achieve the
desired reaction within the flowing suspension, to achieve the desired
particle surface
chemistry, to achieve the desired adherence to gas bubbles, and to achieve the
desired
sorting of the aerated (gas bubble added) suspension particulates according to
size,
density and/or surface characteristics before entering the open vessel of the
hydrocyclone.
In the open vessel, the suspension assumes the form of a swirl path which
splits into an
aqueous underflow, containing coarse or dense or un-aerated, mostly
hydrophilic
particles, and an aqueous overflow containing fine or light and mostly
hydrophobic
aerated particles in the form of a froth.
In addition, one or more obstructions may be placed in the helical conduit to
create turbulence in part of the conduit to thoroughly mix the added fluid
locally with the
suspension flowing in the conduit. The purpose of such an obstruction is to
disrupt
momentarily the sorting that takes place within the conduit in a centrifugal
force field and
to thoroughly mix at least part of the suspension with the injected fluid,
after which the
centrifugal force field in the conduit resumes its sorting influence on the
suspension.
In some cases only one fluid may be injected through the wall of the conduit
of a
first hydrocyclone that is placed in series with one or more other
hydrocyclones. Such a
series configuration will produce an underflow and an overflow from this first
hydrocyclone that will differ from the underflow and the overflow of a
subsequent
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Jan Kruyer, Thorsby, Alberta, Canada
hydrocyclone. The underflow or the overflow of the first hydrocyclone may then
enter
the conduit of a second hydrocyclone where a different fluid may be injected
through the
conduit wall to produce yet another overflow and underflow that differ in
composition
from each other and from the underflow or overflow of the first hydrocyclone.
In this
manner two or more hydrocyclones of the present invention may be placed in
series and
the underflow and overflow of each hydrocyclone may differ in composition and
flow
rate from the underflow and overflow of a preceding hydrocyclone to achieve
the
objective of the present invention for the separation of a suspension.
The conduit ahead of the open vessel or drum of the hydrocyclone may be in the
form of a pipe, a tube with round, square or rectangular cross section, or a
hose, all of
which may be formed into a coil or a spiral. Since a coil generally has a
constant
curvature, the force field within the suspension along coil length will be
constant for a
given flow rate of aqueous suspension in the coil. However, in the case of a
spiral, the
rate of curvature increase from beginning to end. Hence, the force field
within the
suspension along the spiral length for a given flow rate of suspension will
increase
progressively until the suspension reaches the inlet to the open vessel of the
hydrocyclone.
In many cases there may be a further important benefit of providing a helical
conduit ahead of the open vessel of the hydrocyclone since the pressure in the
suspension
at the entrance of the conduit always is greater than the pressure in the
suspension leaving
the conduit and entering the open vessel. For example, when very small air
bubbles are
injected in the suspension near the beginning of the conduit, these bubbles
will expand as
the pressure gradually decreases further down the conduit. Similarly, when a
liquid
under pressure containing a dissolved gas is injected through the wall of a
helical conduit
into the suspension nearer the entrance of the conduit, this gas may come out
of solution
to form gas bubbles that progressively increase in diameter further down the
conduit
towards the open vessel of the hydrocyclone where the pressure in the flowing
suspension is lower.
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SUMMARY OF THE INVENTION
Accordingly, the present invention relates to froth flotation of an aqueous
suspension
in a centrifugal force field in one hydrocyclone or in several hydrocyclones
in series, each
hydrocyclone having a curved conduit in the form of a coil or spiral ahead of
the
hydrocyclone open vessel, in which each open vessel has an underflow outlet
and has an
overflow outlet that is operatively connected to a vortex finder inside each
hydrocyclone
open vessel.
The aqueous suspension to be processed by the present invention is a pumped
suspension or is a flowing suspension stream under pressure which stream may
comprise a
suspension of oil sand ore that has been digested in water prior to entry into
the conduit. It
may comprise an oil sands middlings stream, an oil sands primary tailings
stream, an oil
sands secondary tailings stream, an oil sands tailings pond fluid tailings
(sludge) stream, an
oil sands aqueous stream from the upper levels of a tailings pond that
contains the remains of
undesirable solids in suspension; or it may be a suspension stream from the
bottom of an oil
sands tailings pond dredged from the bottom of the pond, or pumped out of the
pond.
Alternately, the suspension may be an aqueous suspension of comminuted,
crushed
or ground mineral ore that contains valuable minerals and gangue from which
the minerals
are to be separated by flotation, or from which the gangue is to be separated
by flotation
from the minerals by the methods of the present invention. Alternately yet, it
may be a
suspension of salts, plastic particles, or comminuted recycle materials that
may be separated
into two or more components by the methods of the present invention.
FURTHER PROCESSING
The overflow product from a hydrocyclone of the present invention may contain
air and
water and undesirable residual minerals that preferably are removed before the
product is
used or processed further. Such removal may be achieved by passing the
overflow product
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Jan Kruyer, Thorsby, Alberta, Canada
through an aperture oleophilic wall as described in the prior art of the
present inventor or as
described in the above referenced copending patent applications entitled
"Endless Cable
System and Associated Methods, " and "Design of Endless Cable Multiple Wrap
Bitumen
Extrtactors ". When an aerated oleophilic froth is passed through an aperture
oleophilic wall,
water and air may be removed from the froth, and this in many cases will yield
a dryer and
more fluid product that contains little or no air and has a lower water
content. In some cases
the apertured oleophilic wall also will remove some solids that are less
hydrophobic than the
bulk of the froth, especially when the froth is agglomerated in an
agglomerating drum
described in the above referenced copending patent applications.
There has thus been outlined, rather broadly, various features of the
invention so that
the detailed description thereof that follows may be better understood, and so
that the present
contribution to the art may be better appreciated. Other features of the
present invention will
become clearer from the following detailed description of the invention, taken
with the
accompanying claims, or may be learned by the practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. I A is a side view of a hydrocyclone with a conduit in the form of a coil
and an
open vessel with a conical bottom for an axial underflow outlet. FIG. I B is a
plan view of
the same. FIG. 1 C is a side view of a hydrocyclone with a conduit in the form
of a coil and
an open vessel with a conical bottom for a tangential underflow outlet. FIG. 1
D is a plan
view of the same.FIG. I E is a side view of a hydrocyclone with a conduit in
the form of a coil
and an open vessel of generally constant diameter and with a tangential
underflow outlet. FIG.
1 F is a plan view of the same.
FIG. 2A is a side view of a hydrocyclone with a conduit in the form of a
spiral and an
open vessel with a tangential underflow outlet. FIG. 2B is a plan view of the
same. FIG. 2C is
an internal view of a section of the conduit.
FIG. 3A is a side view of a hydrocyclone with a conduit in the form of a
spiral and an
open vessel with a tangential underflow outlet at the bottom and an axial
overflow outlet at the
top. FIG. 3B is a side view of a hydrocyclone with a conduit in the form of a
spiral and an open
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Jan Kruyer, Thorsby, Alberta, Canada
vessel with a tangential outlet at the bottom and an axial overflow outlet at
the bottom. FIG. 3C
is a side view of a hydrocyclone with a conduit in the form of a spiral and an
open vessel with a
conical axial underflow outlet at the bottom and an axial overflow outlet at
the top. FIG. 3D is a
graph of the rise velocity of a bitumen droplet as a function of drop diameter
in a Clark process
PSV in which fresh water was used for producing the oil sand slurry, comparing
the rise
velocity of bitumen droplets in a slurry containing conventional caustic soda
process aid and
the corresponding rise velocity of biutmen droplets in a slurry not containing
any process aid.
FIG. 4A is a plan view of a hydrocyclone with a conduit in the form of a
spiral showing
flange connections within the spiral. FIG. 4B to 4D are enlarged internal
views to better
illustrate these Figures. FIG. 4B is an internal view of a section of the
conduit of FIG. 4A near
a set of flanges, which are provided with a straight flange insert to provide
disturbance and
mixing in the conduit. FIG. 4C is an internal view of a section of the conduit
of FIG. 4A near a
set of flanges, which are provided with a bent plate attached to the flange
insert to provide
disturbance and mixing in the conduit. FIG. 4D is an internal view of a
section of the conduit
of FIG. 4A near a set of flanges, which are provided with a ventury type
attachment to the
flange insert to provide disturbance and mixing in the spiral. FIG. 4E is an
end view of the
insert of FIG. 4B not drawn to scale. While FIGs. 4B to 4D make reference to
FIG. 4A which
uses a spiral conduit, these three Figures (B to D) may also represent the use
of obstructions in
a conduit that is in the form of a coil.
FIG. 5 is side view of a hydrocyclone with a conduit in the form of a spiral
and an open
vessel with an overflow outlet at the bottom feeding the agglomerating drum of
an oleophilic
apertured wall separator to remove air, water, solids from the hydrocyclone
overflow. It is of
note to mention that for the sake of convention, the bottom and top of a
hydrocyclone are
described here as though the open vessel is mounted in an upright position.
However, the
hydrocyclones of the present invention may be mounted in any direction,
vertical, horizontal or
at an angle, since the centrifugal force field in the hydrocyclones of the
present invention
normally is much larger than the force field due to gravity.
FIG. 6 is a flow diagram of an apertured oleophilic wall separator operatively
connected with the helical conduit of a hydrocyclone of the present invention
to recover
bitumen from sludge by the separator followed by a preliminary bitumen product
clean up by
the hydrocyclone system.
FIG. 7 is a flow diagram of two hydrocyclones in series.
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Jan Kruyer, Thorsby, Alberta, Canada
It will be understood that the above figures are simplified and are merely for
illustrative purposes in furthering an understanding of the invention without
in any way
limiting any applications or aspects of the invention. Further, the figures
are not drawn to
scale, thus dimensions and other aspects may, and generally are, exaggerated
or changed to
make illustrations thereof clearer. Therefore, departure can be made from the
specific
dimensions and aspects shown in the figures in order to produce the
hydrocyclones of the
present invention.
DETAILED DESCRIPTION
Before the present invention is disclosed and described, it is to be
understood that this
invention is not limited to the particular structures, process steps, or
materials disclosed
herein, but is extended to equivalents thereof as would be recognized by those
ordinarily
skilled in the relevant arts. It should also be understood that terminology
employed herein is
used for the purpose of describing particular embodiments only and is not
intended to be
limiting.
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. Thus, for example, reference to "a pump" includes one or more of
such pumps,
reference to "an elbow" includes reference to one or more of such elbows, and
reference to
"injecting" includes reference to one or more of such actions.
DEFINITIONS:
In describing and claiming the present invention, the following terminology
will
be use herein in accordance with the definitions set forth below.
Aerated refers to containing gas. An aerated froth is a froth that contains
gas
which gas may be air or any other type of gas suitable for achieving the
objectives of the
present invention.
Agglomerator or agglomeration drum refers to a revolving drum containing
oleophilic surfaces that is used to increase the particle size of bitumen in
an aqueous
suspension prior to separation. Bitumen particles flowing through the drum
come in contact
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Jan Kruyer, Thorsby, Alberta, Canada
with the oleophilic surfaces and adhere thereto to form a layer of bitumen of
increasing
thickness until the layer becomes so large that shear from the flowing
suspension and from
the revolution of the drum, and of the bed of balls, causes a portion of the
bitumen layer to
slough off, resulting in bitumen particles that are much larger than the
original bitumen
particles of the slurry.
Apertured refers to a wall that has one or more apertures depending on the
function
of the aperture or apertures. For example, an apertured aggomerator
cylindrical wall has a
multitude of apertures to allow the flow of bitumen or tailings. On the other
hand, an
apertured helical conduit may only have one or more apertures passing through
the conduit
wall when one or more nozzles are mounted in the helical conduit for injecting
of a fluid into
the suspension flowing through the conduit. In both cases, the drum wall and
the conduit are
apertured, since each wall has at least one aperture passing through the wall.
Bitumen refers to a viscous hydrocarbon, including maltenes and asphaltenes,
that is
found in oil sands ore interstitially between the sand grains. In a typical
oil sands plant, there
are many different streams that may contain bitumen. Bitumen may also refer to
any heavy
viscous hydrocarbon. As the result of processing, bitumen may be suspended in
water in the
presence of particulate solids. Bitumen normally has a specific gravity close
to 1.0 but may
be denser when it contains captured solid particulates in the bitumen phase
particles.
Central location refers to a location that is not at the periphery,
introductory, or exit
areas. In the case of a pipe, a central location is a location that is neither
at the beginning of
the pipe nor the end point of the pipe and is sufficiently remote from either
end to achieve a
desired effect, e.g. washing, reacting with or disrupting agglomerated
materials, etc.
Centrifugal force field refers to a force field that is generated inside a
helical
conduit or inside a hydrocyclone open vessel due to a suspension in the
conduit or in the
vessel flowing in a helical or circular path.
Conditioning in reference to mined oil sand is consistent with conventional
usage
and refers to mixing a mined oil sand with water, air and caustic soda to
produce a warm or
hot slurry of oversize material, coarse sand, silt, clay and aerated bitumen
suitable for
recovering bitumen froth from said slurry by means of froth flotation. Such
mixing can be
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Jan Kruyer, Thorsby, Alberta, Canada
done in a conditioning drum or tumbler or, alternatively the mixing can be
done as it enters
into a slurry pipeline and/or while in transport in the slurry pipeline.
Conditioning aerates
the bitumen for subsequent recovery in separation vessels, e.g. by flotation.
Likewise,
referring to a composition as "conditioned" indicates that the composition has
been subjected
to conditioning.
Conduit refers to a pipe, a tube or a hose that confines an aqueous
suspension, which
suspension may flow due to a pressure difference between inlet an outlet of
the conduit. A
helical conduit is a pipe, a tube or a hose that is formed into the shape of a
coil or in the
shape of a spiral.
Confined, or confines, refers to a state of substantial enclosure. A path of
suspension
may be confined if the path is, e.g., walled or blocked on a plurality of
sides, such that there
is an inlet and an outlet and a direction of the flow which is determined by
the shape and
direction of the confining material. Although typically provided by a pipe,
tube, hose or
baffles, other features can also create a confined path.
Cylindrical indicates a generally elongated shape having a substantially
circular
cross-section. Therefore, cylindrical includes cylinders, conical shapes, and
combinations
thereof. The elongated shape has a length referred herein to as a depth
calculated from one
of two points - the open vessel inlet, or the defined top or side wall nearest
the open vessel
inlet.
Disengagement and digesting of an oil sand ore or slurry are used
interchangeably,
and refer to a primarily physical separation of bitumen from sand or other
particulates in
mined oil sand slurry. Disengagement of bitumen from oil sands occurs when
physical
forces acting on the oil sand slurry results in the at least partial
segregation of bitumen from
sand particles in an aqueous medium and may not necessarily require a process
aid.
Endless cable belt when used in reference to separations processing refers to
an
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. Movement of the endless cable
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 onto a drum or roller. The
apertures in
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Jan Kruyer, Thorsby, Alberta, Canada
the endless belt are the slits or gaps between sequential wraps. The endless
cable can be a
wire rope, a plastic rope, a metal cable, a single wire, compound filament or
a monofilament
which is spliced together to form a continuous loop, e.g. by splicing. As a
general guideline,
the diameter of the endless cable can be as large as 2 cm and as small as
0.001 cm, although
other sizes might be suitable for some applications. An oleophilic endless
cable belt is an
endless cable belt made from a material that is oleophilic under the
conditions at which it
operates.
Fines refers to suspension particles that are not larger than 45 microns on
average.
Fines normally pass through a mesh screen that has 45 micron square openings.
Fluid in these specifications specifically refers to a liquid or a gas or to
liquid and gas
mixtures injected through nozzles or through apertured conduit sections
directly through the
conduit wall into the flowing suspension.
Fluid tailings are aqueous suspensions representing tailings from an oil sands
plant from which coarse solids, such as sand, have been removed. The term fine
tailings has
replaced the old term of tailings pond sludge but has the same meaning as
fluid tailings.
Because of the confusion of terms used for oil sand tailings in the oil sands
industry, for the
present invention, fluid tailings sludge is a name used for sludge or for
fluid tailings. See
"sludge" for further clarification.
Helical conduit or conduit refers to a conduit, pipe, tube or hose formed into
a spiral
or a coil shape including multiple generally circular loops. Consistent with
this definition, a
"helical path" is a path which follows a helical shape and is generally
"confined" to such a
path by physical barriers such as pipe walls. Such helical shape can include a
coil shape,
wherein the shape mostly represents a stretched spring. Alternatively, the
helical shape can
include a planar helical shape, known as a spiral, wherein the path may be
(but does not have
to be) in a single plane and is a curve which emanates from a central point,
getting
progressively farther away as it revolves around the point, such as the spiral
conduit shown
in FIG. 2B. In terms of flow path, the flow gets progressively closer to the
central point in
such spiral embodiments.
Hydrocyclone may at times be used interchangeably with "separating apparatus,"
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Jan Kruyer, Thorsby, Alberta, Canada
where both terms indicate the equipment, as described herein, beginning with
the helical
conduit and including the open vessel with an underflow and an overflow.
Open vessel or drum of a hydrocyclone refers to a vessel which is
substantially free
of internal structures and/or obstructions other than those explicitly
identified as present, e.g.
a vortex finder. An open vessel, as used herein, can often be a completely
vacant cylindrical
vessel having various inlets and outlets as identified, with substantially no
other structures
present within the vessel other than a vortex finder.
Operatively associated with refers to any functional association which allows
the
identified components to function consistent with their intended purpose. For
example, units
such as pumps, pipes, vessels, tanks, etc. can be operatively associated by
direct connection
to one another or via an intermediate connection such as a pipe or other
member. Typically,
in the context of the present invention, the units or other members can be
operatively
associated by fluid communication amongst two or more units or devices. The
term
"operatively connected to" has a similar meaning but it is more specific. For
example when
a conduit is operatively connected to an open vessel inlet it implies that the
outlet of the
conduit is connected to the inlet of the open vessel smoothly so as to
optimize the operation
of the conduit and to optimize the operation of the open vessel. Similarly,
when an overflow
outlet is operatively connected to a vortex finder it implies that the
connection between
vortex finder and outlet is such as to optimize the operation of the vortex
finder and to
optimize the operation of the overflow outlet.
Overflow refers to a more central portion of a swirl flow, and as such, is
often the
more valuable fluid containing fines and bitumen, and/or valuable minerals.
Alternately the
overflow may consist of gangue.
Series represents a number of more than two. A series of nozzles, for example,
can
be three nozzles, four nozzles, five nozzles, etc. The series of nozzles can
be regularly
placed or irregularly placed, with respect to distance between nozzles.
Sludge is the generic name used in the present invention for any fluid
tailings
suspension that has resided for any time in a mined oil sands tailings pond.
Sludge includes
fresh fine tailings that may have just arrived in the pond, fine tailings that
have resided in the
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
pond for over a year, and mature fine tailings that have resided in the pond
for one or several
decades. The main difference between fresh fine tailings and fine tailings is
that fine tailings
have a lower water content than fresh fine tailings. Similarly, mature fine
tailings have a
lower water content than fine tailings. Besides sludge giving up water with
time in the pond,
microbial action in sludge occurs when the sludge matures or ages in the pond.
Such
microbial action results in the formation of gases and changes in the bitumen
chemistry of
the sludge. Fresh fine tailings may also be tailings from which coarse solids,
such as sand,
have been removed but which have not entered a tailings pond.
Swirl path refers to a flow pattern inside an open vessel or drum which
generally
follows an unconfined helical path, although significant mixing and chaotic
flow may occur
along the axis of overall flow down the length of the vessel or drum. A swirl
path is
generally produced by introducing fluids tangentially into a generally
cylindrical vessel thus
producing flow circumferentially as well as longitudinally down the vessel
length. A swirl
path refers to an unconfined, generally helical, swirl flow inside an open
vessel.
Underflow refers to a more circumferential portion of a swirl flow and
typically
contains coarser material and is often drawn off as effluent and/or for
further processing. In
many cases the underflow contains predominantly hydrophilic particulates in
water. Often, a
fluid processed by a hydrocyclone is split into a single overflow and single
underflow,
although multiple overflow and/or underflows may be issue when hydrocyclones
are placed
in series.
Velocity is used 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 are
specifically defined
to have substantially constant or gradually changing bulk directional
velocity.
Vortex finder refers to a centrally located pipe within a hydrocyclone open
vessel
for the purpose of removing overflow from the hydrocyclone. The vortex finder
can be a
simple pipe having an unrestricted open pipe entrance and, alternately may be
provided with
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Jan Kruyer, Thorsby, Alberta, Canada
a flange at the pipe entrance as well, to encourage overflow to find its way
from the open
vessel hydrocyclone interior into the vortex finder opening. A vortex finder
normally is
operatively connected to an overflow outlet of the open vessel.
Substantially refers to the complete or nearly complete extent or degree of an
action,
characteristic, property, state, structure, item, or result. For example, an
object that is
"substantially" enclosed would mean that the object is either completely
enclosed or nearly
completely enclosed. The exact allowable degree of deviation from absolute
completeness
may in some cases depend on the specific context. However, generally speaking
the
nearness of completion will be so as to have the same overall result as if
absolute and total
completion were obtained. The use of "substantially" is equally applicable
when used in a
negative connotation to refer to the complete or near complete lack of an
action,
characteristic, property, state, structure, item, or result.
A plurality of components may be presented in a common list for convenience.
However, these lists should be construed as though each member of the list is
individually
identified as a separate and unique member. Thus, no individual member of such
list should
be construed as a de facto equivalent of any other member of the same list
solely based on
their presentation in a common group without indications to the contrary.
Concentrations, amounts, volumes, and other numerical data maybe 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 cm to about 5 cm" should be interpreted to include not only the
explicitly recited
values of about 1 cm to about 5 cm, 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 numerical value. Furthermore, such an
interpretation
should apply regardless of the breadth of the range or the characteristics
being described.
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Jan Kruyer, Thorsby, Alberta, Canada
Consistent with this principle the term "about" further includes "exactly"
unless otherwise
stated.
EMBODIMENTS OF THE INVENTION
It has been found that fluids having components of different densities, of
different
surface chemistry and/or containing different particle sizes, particularly
those including
mineral particulates and liquid, can be effectively separated using a
hydrocyclone having a
helical conduit immediately upstream of a substantially cylindrical open
vessel.
Hydrocyclones can be used as a separating mechanism for a variety of
suspensions.
However, the hydrocyclones of the present invention can be particularly suited
to the
replacement of conventional gravity induced froth flotation for the separation
of liquid
suspensions by imposing a much greater separation force on the suspension than
is possible
by gravity alone. Not only can the imposed separation force field in a
hydrocyclone be much
greater than is possible with conventional gravity induced froth flotation,
but the use of a
helical conduit ahead of the hydrocyclone drum also allows for the
introduction of various
fluids, through the conduit wall, including gasses, activators, promoters,
suppressants,
frothers and other chemicals into the suspension while the flowing suspension
is exposed to a
centrifugal force field that is much greater than the force of gravity alone.
The suspension
flowing through the helical conduit is exposed to a centrifugal force field
and also is
confined in the conduit under pressure which pressure gradually decreases as
the suspension
flows through the conduit from entrance to exit before it enters the
hydrocyclone open vessel
through its entrance to become part of the swirl region within the
hydrocyclone open vessel
to be subsequently separated into an underflow stream and an overflow stream.
In accordance with the above discussion, various embodiments and variations
are
provided herein which are applicable to each of the apparatus, fluid flow
patterns, and
methods of separating components of a suspension described herein. Thus,
discussion of one
specific embodiment is related to and provides support for this discussion in
the context of
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Jan Kruyer, Thorsby, Alberta, Canada
the other related embodiments.
As a general outline, a hydrocyclone can include a substantially open
cylindrical
vessel with an open vessel inlet. The open vessel inlet can be configured to
introduce a fluid
tangentially into the open vessel. In a specific embodiment, the open vessel
inlet connecting
the helical conduit to the open vessel can be configured to introduce the
fluid into the open
vessel with minimal disturbance in fluid flow in the transition between the
conduit and the
open vessel. Thus the hydrocyclone can include a helical conduit connected
upstream of the
open vessel at the open vessel inlet. An overflow outlet and an underflow
outlet can be
operatively attached to the open vessel wall. The underflow outlet can be
attached at a
location on the open vessel substantially opposite the helical conduit and
open vessel inlet.
The overflow outlet can terminate, on one end, at a vortex finder positioned
in an interior of
the open cylindrical vessel. The overflow outlet can further include a
substantially enclosed
conduit from the vortex finder to an exterior outlet of the open cylindrical
vessel.
Several embodiments of a hydrocyclone in accordance with the present invention
including a helical conduit in the form of a coil are shown in FIGs. 1 A to
FIG. 1 E including
a helical path 100 connected to a substantially open cylindrical vessel 101 at
an open vessel
inlet 102. The embodiments further include underflow outlets 103 attached to
the open
vessel substantially opposite the helical conduit 100. The underflow outlets
103 illustrated
are oriented to match the residual helical flow within the open vessel to
facilitate removal of
underflow fluids. In the case of FIG. IA the open vessel bottom 104 is conical
and the
underflow suspension leaves axially through the bottom 105 of the conical part
104 of the
open vessel. In the case of FIG. 1C, the open vessel bottom 106 also is
conical but the
underflow suspension leaves tangentially through an outlet 107 of the bottom
of the conical
part of the open vessel. In the case of the case of FIG. I E, the underflow
leaves tangentially
through a bottom outlet 108 of the open vessel that does not have a conical
bottom section
but remains of a generally constant diameter. The external overflow outlets
illustrated are
operatively connected to internal vortex finders inside the open vessel. In
the case of FIGs.
1 A,1 B,1 C and 1 D the vortex finders 112 and 113 are operatively connected
to overflow
outlets 109 and 110 attached to the top of the open vessels 101 concentric
with the conduit
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Jan Kruyer, Thorsby, Alberta, Canada
100. In FIGs. I E and I F the vortex finder 114 is operatively connected to an
overflow outlet
111 attached to the bottom of the open vessel 101. The vortex finders 112, 113
and 114 can
be positioned centrally (axially) within the open vessels 101 and can be
further positioned at
a depth that is central or such depth can be adjusted based on the particular
suspension
velocity, composition and other variables to maximize separation of the
suspension into a
suitable underflow and a suitable overflow. Although not always required, as
can be seen in
FIGs. IA to IF, outer diameters of the helical conduit 100 and the open vessel
101 are
substantially the same, at least where these two members are joined. FIGs. IA
to IF also
illustrate the inlets 116, 117 and 118 where the suspension to be separated
can be fed into the
inlet of the helical conduits of the hydrocyclones. Further, the Figures
schematically show
fluid inlets or nozzles 120 which allow the injection of fluids into the
conduits to further
enhance subsequent separation of the suspension in a centrifugal force field.
The fluid inlets
120 may be configured to inject fluid perpendicularly into the path of the
suspension flowing
through the conduit or may be directed for tangential injection of fluid into
the suspension or
alternately may be directed at an angle for injection of fluid into the
suspension with or
against the direction of flow of the suspension to allow the desired mixing of
fluid with
suspension.
The helical conduit situated upstream of the open vessel can serve at least
three
purposes. First, it can be configured to cause a suspension to at least
partially separate, or
begin the separation process prior to entering the open vessel. Second, the
helical conduit
can cause suspension to travel in a path that encourages further separation
and easier
transition once introduced into the open vessel. Third, fluid injected into
the supension along
the periphery of the helical conduit can react with the surfaces of the
particulates in the
suspension and activate, promote or suppress the hydrophobicity of these
particles and cause
separation of these particles by froth flotation in a centrifugal force field
that is more
effective and faster than froth flotation in a conventional flotation cell. As
such, parameters
such as the size and configuration of the helical conduit, the direction and
location of fluid
injection points along the helical conduit, the dimensions of the open vessel,
and the open
vessel inlet can affect processing. The number of rotations of the helical
conduit can, for
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
some fluids, allow for a shorter or longer time spent in the open vessel to
produce the same
level of separation. In a specific embodiment, the helical conduit can wind
for about 2 to
about 10 full rotations. In a further embodiment, the helical conduit can wind
for about 3 to
about 5 full rotations.
The helical conduit can also be formed in a variety of ways from pipe, from
tube or
from hose, and the tube may be circular in cross section or may have a square
or rectangular
cross section. Other types of conduits may be used as well. For example,
complementary
structural channels may be rolled to the desired curvature and welded together
to form
conduits of square or rectangular cross section, described in more detail in
copending
Canadian patent application entitled "Hydrocyclone and Associated Methods ".
The inlet to the helical conduit is at one end of the helical conduit and is
the primary
source of introducing the suspension into the hydrocyclone of the present
invention. The
suspension travels through the helical conduit and leaves from the conduit to
flow into the
open vessel through the open vessel inlet. Components of the fluid are
separated and
removed through the underflow outlet and through the overflow outlet of the
open vessel.
As mentioned previously, the fluid injected through conduit wall into the
suspension
flowing in the conduit can include liquids containing or consisting of
chemicals commonly
classified as activators, promoters, frothers or suppressants, or may include
a gas, a
hydrocarbon or may also include a mixture of steam and air or a mixture of
compressed gas
dissolved in water under pressure. In most cases the fluid injected through
the conduit wall is
at a higher pressure than the suspension flowing through the conduit in the
fluid injection
region. After injection into the suspension, gasses dissolved in the injected
fluid will come out
of solution in the form of gas bubbles when this fluid mixes with the
suspension in the conduit,
and these gas bubbles will expand in size as the suspension pressure decreases
down the
conduit on its way to the hydrocyclone open vessel. In some cases, two or more
chemicals may
be injected as fluids through separate nozzles or through separate porous
sections of the
conduit wall into the suspension, which chemicals may react with each other
upon contact to
achieve the objective of the present invention to promote froth flotation in a
centrifugal force
field. For example two fluids combining may result in a desired chemical
reaction or may form
gas bubbles in the suspension to which hydrophobic particles (including
bitumen if present)
may attach to enhance froth flotation in the present invention. As another
example, milk of lime
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Jan Kruyer, Thorsby, Alberta, Canada
may be the injected fluid which may react with the contents of the suspension
flowing through
the conduit. In this case both the liquid in the conduit and the injected
fluid are suspensions of
solid particulates in water. A similar fluid may be a suspension of gypsum in
water. Using
suspensions of this nature as the fluid may allow for faster chemical
reactions in the conduit
than using dissolved lime or dissolved gypsum in water only, since water can
only hold a small
amount of dissolved lime or gypsum.
The use of a conduit in the form of a spiral is illustrated in FIG. 2. A side
view is
shown in FIG. 2A and a plan view is shown in FIG. 2B. A suspension under
pressure flows
from a feed pipe 201 into the inlet 202 of the spiral. The feed pipe may be
connected to the
spiral conduit 204 by means of flanges 203 or by some other means, such as,
for example, by
welding. Nozzles 205 are mounted into the wall of the spiral conduit to allow
for injection
of fluid into the suspension as it travels through the conduit 204. The spiral
conduit connects
smoothly to the open vessel 208 of the hydrocyclone and, as a result, the
suspension leaves
the conduit 204 and enters the open vessel 208 with a minimum amount of flow
disturbance
to continue the flow and become a swirl path in the open vessel until the
suspension splits
into two streams, the overflow, and the underflow. Overflow outlet 207 and
underflow
outlet 206 are shown in FIGs. 2A and 2B. The overflow outlet 207 is
operatively connected
to a vortex finder 210 inside the open vessel 208.
FIG. 2C is an internal view of a section of the spiral conduit 204, showing an
inside
lane 215 and an outside lane 216. It also provides an illustration of the
contents of the
suspension in the conduit 204 where coarse un-aerated particulates gravitate
towards the
outside lane and aerated particles gravitate towards the inside lane. This is
the result of the
centrifugal force field in the conduit and of gas bubbles injected as the
fluid 220. The
hydrophobic (oleophilic) particles adhere to the gas bubbles and cause these
particles to
gravitate towards the inner lane under the influence of the centrifugal force
field operating in
the flowing suspension in the conduit. In FIG. 2C the gas bubbles are
illustrated in the form
of open circles to which are attached small black particles, indicating
bitumen droplets or
hydrophobic mineral particles. In the enclosed Figures nozzles are used to
illustrate the flow
of fluid through conduit walls. However porous or aperture wall sections in
the conduit in
some cases may serve the same purpose, or a more effective purpose than
nozzles in some
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Jan Kruyer, Thorsby, Alberta, Canada
cases.
All this is in contrast with the above referenced copending US patent
application
"Removal of Bitumen from Slurry Using a Scavenging gas ", filed June 3, 2008,
in which the
amount of gas injected into the conduit was kept at a minimum in an effort to
minimize or
eliminate the production of froth from the hydrocyclone overflow. It was the
objective of
that copending application to allow the bulk of the suspension to absorb the
injected gas
before the overflow left the hydrocyclone open vessel. The present invention
has the
opposite objective of adding an abundance of gas to the suspension in the
conduit and to
produce an overflow from the hydrocyclone that contains an abundance of froth.
Hence,
FIG. 4 of the copending referenced US patent application shows a much smaller
number of
gas bubbles in the suspension flowing through the conduit, as compared with
the much larger
number of gas bubbles in the suspension flowing through the conduit of FIG. 2C
of the
current patent application. The gas bubbles in the Figure are illustrated by
open circles and
most of the bubbles have a hydrophobic particle attached to them, illustrated
in the form of
black dots.
For a suspension containing solids that have a higher density than the
suspension
liquid, the centrifugal force field in the suspension flowing through the
helical conduit causes
the gradual movement of solids towards the outer lane with minimal disturbance
of the
flowing suspension. Furthermore, for a constant suspension flow rate, the
centrifugal force
field in a conduit in the form of a coil tends to be constant. In contrast,
for a constant
suspension flow rate, the centrifugal force field gradually increases as the
suspension travels
in a conduit that has a progressively increasing curvature between conduit
inlet and open
vessel inlet, such as in a spiral. In a spiral conduit, the coarse and heavy
solids initially move
to the outside lane, when the centrifugal forces are relatively small, Then
gradually, as the
centrifugal force field increases, this layer of solids increases in thickness
as the smaller and
lighter solids progressively move towards the outer lane and deposit on top of
and fill the
voids between the coarse solids. In this manner, a relatively smooth
transitional sorting of
the solids takes place while the slurry is flowing through a helical conduit
in the form of a
spiral. After the suspension enters the open vessel through a low disturbance
entrance, the
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CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
bed of coarse solids can continue to flow along the outer periphery of the
open vessel in the
form of a swirl path and report to the underflow while the coarse-solids-
depleted suspension
reports to the overflow and contains all, or nearly all the froth and a
portion of the fines of
the suspension.
It is well known that in centrifuges there are very high shear forces that
exist at the
point where the suspension enters the bowl via the axial feed and is
accelerated to the bowl
speed. Similar shear forces, although perhaps to a lesser extent, occur near
the tangential
inlet of conventional hydrocyclones where the linearly moving suspension is
rapidly
converted into a suspension moving in a helical flow path. Such a drastic
conversion does
not occur in the hydrocyclones of the present invention since a helical flow
path is already
well established in the conduit before the suspension enters the open vessel.
The nozzles or porous conduit wall sections that supply fluid to the helical
conduit
serve to, for example, introduce an abundance of gas bubbles that aerate
bitumen of the
suspension flowing through the conduit and that also scavenge bitumen droplets
and/or
hydrophobic solids out of the voids in the bed of solids flowing along the
outside lane of the
conduit and thereby help in transferring these to the suspension stream in the
middle or
inside lane of the conduit, the bulk of which may leave the hydrocyclone
through the
overflow. While this discussion mainly centered around the benefits of a
helical conduit in
the form of a spiral, a similar frothing of bitumen and/or hydrophobic solids
and a similar
transfer of captured bitumen droplets and/or hydrophobic minerals to the
middle and inside
lane of the suspension stream takes place with the help of gas bubbles if
these are introduced
in a helical conduit that has the form of a coil.
The nozzles can be present in a series along the length of the helical coil.
The series
can be regularly or irregularly spaced. Typically, a nozzle can be mounted at
a location
along the outer wall of the helical conduit, but it may also be mounted along
the inner wall or
along any other position of the cross section of the conduit. A variety of
nozzles can be used
in the design of the separating apparatus. In one aspect, the series of
nozzles can be designed
for sonic gas flow through the nozzles, where each nozzle is configured to
produce local
cavitation and gas dispersion upon the gas entry into the helical conduit. In
another aspect
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Jan Kruyer, Thorsby, Alberta, Canada
the fluid may be a liquid containing compressed gas that releases from the
fluid after entry
into the suspension. In yet another aspect the fluid may be a froth flotation
collector,
activator, depressant, frother or modifier, which are common or special
chemicals used in
conventional froth flotation of minerals. In some cases porous sections for
fluid injection
may be mounted between flanges in the helical conduit. Such flange mounting
facilitates
surrounding a porous section with a pressure chamber for containing fluid to
be injected into
the conduit but also provides for convenient replacement or for cleaning
Gas bubbles injected into the conduit may be of various sizes depending on a
large
number of variables, including nozzle design and size, aperture size of porous
conduit
sections, pressure difference between injected fluid and suspension in the
conduit, etc. Small
size gas bubbles are preferred for these have a lower tendency to coalesce. A
high
concentration of very small bubbles sweeping through the suspension will tend
to capture
bitumen or hydrophobic minerals and may dislodge bitumen and/or hydrophobic
minerals
from between coarse hydrophilic solids in the outer lane. Generally, bubbles
can have
diameters smaller than about 3 mm, although bubbles having a diameter smaller
than about
0.3 mm or even smaller than 0.03 mm can be particularly useful in achieving
increased
contact surface area with bitumen and/or hydrophobic minerals of very small
particle size.
One very effective way of producing very small gas bubbles is the use of a
injection fluid
consisting of a mixture of compressed air and steam. Another method of
producing very
small and well dispersed bubbles is to prepare a fluid, such as a water and
gas mixture under
high pressure in a vessel which is then allowed to flow through the conduit
wall into the
suspension. Under high pressure, gasses such as air, air enriched by oxygen,
methane,
ethane, propane, carbon dioxide, or combinations thereof may be dissolved in
large
quantities in liquid, such for example water, under high pressure. When such
high pressure
liquid and dissolved gasses flow through the conduit wall of the instant
invention and
encounter a suspension of lower pressure in the helical conduit, the gasses
may be released in
the form of small bubbles. Many small bubbles of gas released very quickly in
the
suspension may sweep through the voids between the solids in suspension and
may also
transport trapped bitumen and/or hydrophobic solids out of the voids between
coarse
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
hydrophilic solids flowing along the outside lane of the conduit. Since there
is a pressure
gradient in the suspension flowing through the conduit, small gas bubbles near
the entrance
of the conduit will increase in size as these flow through the conduit, enter
the open vessel
and leave as overflow.
Therefore, as outlined above, the instant invention can function to aerate
hydrophobic
particles, including valuable minerals or other minerals or bitumen and also
to transfer such
hydrophobic particles from the outside lane of the conduit into the centre or
inside lane of the
conduit to optimize the subsequent content of these hydrophobic particulates
in the overflow of
the hydrocyclone. In another embodiment of the instant invention, additives,
such as collectors,
activators, depressants frothers, gas and/or flotation modifiers may be
introduced through the
conduit wall into the suspension flowing through the helical conduit to
promote the desired
separation of hydrophobic particulates from hydrophilic particulates by the
hydrocyclones of
the present invention. In some cases these additives may serve to selectively
make some
particulates hydrophilic and selectively make other particulates hydrophobic
and promote
adhesion of these hydrophobic particles to gas bubbles. In fact, the same
surface chemistry
and surface adhesion technology that was developed for convention gravity
induced froth
flotation may be applied to the methods of the present invention that uses
froth flotation under
the influence of a centrifugal force field. Hydrophobic mineral particles,
which particles may
include bitumen particles in some cases, that adhere to gas bubbles are
lighter than mineral
particles without gas bubbles and will rise through a suspension to the top of
a conventional
flotation vessel. Similarly, in a flowing suspension in a helical conduit,
hydrophobic particles
that adhere to gas bubbles are lighter than mineral particles without gas
bubbles and may
gravitate towards the inside lane of the conduit due to the centrifugal force
field operating in the
curved conduit. These density reduced particles will flow through the open
vessel swirl path
and may report to the overflow, while coarse and dense hydrophilic particles
generally will leave
the hydrocyclone through the underflow.
Gas that may be used as the fluid under pressure flowing through the conduit
wall into
the suspension may contain air,oxygen enriched air,a light hydrocarbon gas,
such as methane,
ethane, propane, butane, carbon dioxide, or any combination thereof. The use
of carbon dioxide
may also serve to neutralize an oil sand slurry if it has a pH greater than 7
as the carbon dioxide
is consumed in the suspension producing sodium carbonate or sodium bicarbonate
by reaction
with sodium hydroxide that may be present in, for example an oil sand slurry
Aqueous reagents that may be injected through the conduit wall may also
include
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Jan Kruyer, Thorsby, Alberta, Canada
anionioc collectors, alkyl sulfonates and sulfates, cationic collectors,
amphoteric collectors,
chelating agents, sodium sesquicarbonate, ammonium lignin sulfonate, corn
starch, potato
starch, high molecular weight water soluble gums, portland cement,amine-
aldehyde resins, soda
ash, sodum silicate, alkali phosphate, dextrin, polyhydroxy amines, hot lime,
slaked lime, milk
of lime and aqueous suspensions of finely divided gypsum,
Optionally, one or more nozzle may be mounted in the wall of the open vessel.
Such
nozzles can be configured to inject a gas, a liquid including dissolved gas,
or even a
conventional froth flotation additive into the swirl path in the open vessel.
The helical conduit situated upstream of the open vessel can be configured to
cause a
fluid to at least partially separate, or begin the separation process prior to
entering the open
vessel. Additionally, the helical conduit can cause the fluid to travel in a
path that
encourages further separation and easier transition once introduced into the
open vessel. As
such, parameters such as the size and configuration of the helical conduit,
the number and
location of nozzles or porous conduit sections, the dimensions of the open
vessel, and the
open vessel inlet can affect processing. The number of rotations of the
helical conduit can,
for some fluids, allow for a shorter or longer time spent in the open vessel
to produce the
same level of separation. In a specific embodiment, the helical conduit can
wind for about I
to about 10 full rotations. In a further embodiment, the helical conduit can
wind for about 2
to about 5 full rotations.
The open vessel inlet, which allows flow from the conduit into the open
cylindrical
vessel, can be configured to introduce the fluid with minimal disturbance in
the fluid flow.
For example, the internal surfaces at the connection between the helical flow
conduit and the
open vessel can be a substantially smooth transition where the inside surface
of the helical
conduit smoothly blends into the inside surface of the open vessel. The
confined fluid
exiting the helical conduit may flow smoothly into the open vessel to form the
swirl path that
eventually separates into an underflow and an overflow. Minimal disturbance in
the fluid
flow from the helical conduit to the open vessel allows for greater separation
efficiency.
This configuration further reduces abrasive wear on internal surfaces of the
open vessel. In
particular, initiating the centrifugal force field well ahead of the open
vessel can significantly
reduce wear and abrasion of the open vessel internal walls. The slower flowing
bed of solids
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CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
flowing along the outer wall of the helical conduit will join the open vessel
swirl path at a
slower rate than non-peripheral flow of the suspension. This aspect of the
present invention
provides wear reduction as compared with direct tangential introduction of a
suspension into
an open vessel where the swirl path is established only after the slurry
enters the open vessel.
To aid in fluid flow, in one embodiment, a pump or a plurality of pumps can be
used.
This is particularly useful at the beginning of the helical conduit to cause
the fluid to flow at
a desired velocity which is generally relatively high. Normally a pipe or
pipeline may
provide the suspension to the helical conduit, but pumps can optionally be
additionally used.
However, care in design should be taken in order to prevent or reduce
undesirable
disturbance to flow patterns in suspension entering the open vessel.
In a specific embodiment, a method for separating components from a fluid can
include guiding the fluid through a helical conduit at a high velocity to form
a helically
flowing fluid. The method can further include tangentially injecting the
helically flowing
fluid into an open vessel such that the fluid rotates along a swirl path
within the open vessel.
The fluid rotation in the swirl path, and enhanced by rotation in the helical
conduit, can be
sufficient to produce an overflow and an underflow. Such fluid separation is
based on the
varying densities and varying particle sizes of the components of the fluid.
The method can
additionally include injecting a fluid through walls into at least one of the
helical path and
the swirl path. The overflow and underflow can be removed from the open
vessel.
The fluid in the helical conduit can travel at any velocity sufficient to
produce an
initial separation of the fluid components while in the helical conduit and/or
produce an
overflow and underflow while in the open vessel. Such initial separation can
include
compositional differences across a diameter of flow. Although such velocity
will vary
depending on the design of the hydrocyclone and the fluid to be processed, in
one
embodiment, the magnitude of the velocity of the suspension in the helical
path can be from
about 1 meter per second to about 10 meters per second, and in some cases from
about 2
meters per second to about 4 meters per second.
In a specific embodiment, fluid can be injected into the helical conduit
substantially
prior to the tangentially injecting into the open vessel. For example, fluid
can be injected
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Jan Kruyer, Thorsby, Alberta, Canada
through the wall of the helical conduit at a central location along the
helical conduit between
a fluid inlet to the helical conduit and the open vessel inlet. Such injection
along the helical
conduit can include injection of one or more fluids at a plurality of
locations along the helical
path. Nozzles may alternate with apertured conduit sections or nozzles or
apertured sections
may be used exclusively. Alternative to, or in conjunction with injecting
fluid through the
walls of a helical conduit, fluid of the same or different type, can be
injected into the swirl
path. Such injection of fluid into the swirl path can be substantially
subsequent to injecting
fluid through the conduit wall. For example, the fluid can be injected at
central locations to
the open vessel inlet and the underflow outlet. As with injecting fluid into
the helical
conduit, fluid can be injected into the swirl path at a plurality of locations
through nozzles.
The overflow and underflow will generally contain particulates but will have
different compositions. When processing an oil sand suspension, the overflow
will contain,
ideally, water and bitumen froth and silt and clay particulates which are
small and possibly
of lower density. The underflow, on the other hand, will ideally contain
water, silt, sand, and
particulates which are larger and may also be denser. When processing a
minerals ore
mixture, the suspension to be separated can be an aqueous suspension
containing
particulates. In such case, and depending on the other components in the
suspension, the
underflow can include particulates that naturally are hydrophilic or the
surfaces of these
particulates may have been made hydrophilic by the use of one or more
suppressors or
suppressants injected as a fluid into the helical conduit. Similarly the
overflow may include
a froth of particulates that are naturally hydrophobic, or the surfaces of
these particulates
may have been made hydrophobic by the use of activators, collectors or
modifiers injected as
a fluid into the helical conduit. In addition, gas may have been part of the
injected fluid to
cause the hydrophobic particles to adhere to gas bubbles to lighten them and
cause them to
first move away from the outer lane of the conduit fluid and subsquently
report to the
overflow of the hydrocyclone in the form of froth. The hydrocyclones of the
present
invention are particularly suited to separation of an oil sand suspension or a
bitumen
containing suspension representing a continuous water phase containing
dispersed bitumen
particulates or agglomerates, gravel, sand, silt and clay or a water
suspension of dispersed
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Jan Kruyer, Thorsby, Alberta, Canada
bitumen product and fines. Alternatively, mineral ore slurries can be
effectively separated
using the hydrocyclones described herein. Among others, the fluid injected
through the wall
of the conduit may be air, gas, a liquid containing dissolved gas, a mixture
of air and steam
or may be a suspension in water, such as milk of lime or a suspension of
gypsum dispersed
in water, or similar dispersions in water of divalent or trivalent salts, etc.
One specific use of the hydrocyclone can be in de-sanding fluids containing
bitumen.
In such case, the fluid can include particulates, bitumen, air and water.
Particulates included
in the bitumen-containing fluid can include gravel, sand, and fines. When
processed, the
overflow can include the majority of the bitumen of the fluid in the form of
froth and the
underflow can include the majority of the gravel and sand. In a specific
embodiment, the
overflow can include less than 20% of the particulates in the form of fine
sand and fines.
Unlike the above referenced copending patent application first filed less than
12 months ago,
the amount of gas introduced into the helical conduit of the present invention
is large enough
that the overflow contains a high percentage of froth. This is unlike the
referenced
copending application where the objective was to minimize the amount of gas
added and
thus reduce or eliminate the amount of froth reporting to the overflow of the
hydrocyclone.
The objective of the prior patent was to produce a bitumen product that was
very low in gas
content by allowing gas introduced into the helical conduit to be absorbed in
the bulk of the
suspension fluid of the hydrocyclone before the overflow left the open vessel.
Not all bitumen-containing fluids are the same, and the varying properties of
bitumen-containing fluids need to be considered when designing a particular
hydrocyclone.
Conditions and/or design of the hydrocyclone can be specifically configured
for improved
and optimum processing. In a specific embodiment, the helical conduit and/or
open vessel
can be designed and shaped based on compositional and physical properties of
the fluid.
Therefore, parameters may be adjusted for varying types of bitumen-containing
fluids.
The bitumen-containing fluid can be a result of pre-conditioning of oil sands
and
water. As such, the composition of the fluid can, at least partially, depend
on the
composition of the oil sands. Some oil sands contain a high percentage of
bitumen and low
percentage of fines, while other oil sands contain a moderate or a small
percentage of
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
bitumen and further have a high fines content. Some oil sands come from a
marine deposit
and other oil sands come from a delta deposit, each having different
characteristics. Some
oil sands are chemically neutral by nature and other oil sands contain salts
and other
chemicals that affect, among other things, the pH or the salinity of the
slurry.
Other factors to consider when dealing with oil sands include the composition
of the
rocks and gravel, and lumps of clay in the oil sand after crushing. Not only
the size of the
rocks, gravel and clay lumps but also the percentage of these in the crushed
oil sand, as well
as the shape of the rocks gravel or lumps of clay can affect processing
conditions. Likewise,
the chemical composition of the slurry as it is being processed by the
hydrocyclone can
affect processing. For example, a fluid that has a low pH or a high pH
inherently, or by the
addition of chemicals will have a very different rheological characteristic
than a suspension
that is close to neutral or close to the isoelectric point. The pH of a fluid
can have a
substantial impact upon the dispersion of fines in such a fluid and upon the
resulting
viscosity of the fluid. At high or low pH the clay fines are dispersed,
resulting in low
viscosity fluids in which bitumen particles and the coarse solids are
substantially free to
move and/or settle within the suspension of the separating vessel.
A factor to consider in selecting processing parameters is the velocity of the
fluid as
it flows through the hydrocyclone, and through the helical conduit in
particular. For a given
pump capacity, a different pipe size will result in a different fluid velocity
in the
hydrocyclone. Therefore, multiple pumps can be used in some embodiments ahead
of the
conduit (rather than in or after the conduit which would create undesirable
disturbance to the
flow path).
Processing time for fluids differs greatly depending on the helical conduit,
open
cylindrical vessel, fluid, desired processing, etc. As a non-limiting example,
however, the
fluid can have an average residence time in the hydrocyclone, from
introduction into the
helical conduit, until removal as either underflow or overflow of from about 1
second to
about 30 seconds, and in some cases from about 4 seconds to about 10 seconds.
Therefore, as outlined above, the instant invention can function to separate
components of suspensions. The fluids injected into the suspensions may be
water, flotation
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Jan Kruyer, Thorsby, Alberta, Canada
modifiers, other chemicals dissolved in water, hydrocarbons and gasses,
including air, as the
froth producing reagent fluids. Additionally, the combination of a helical
conduit and open
vessel gives greater control over separation and fluid flow than does
separation by means of
one or the other portions of the hydrocyclone alone.
FIGs. 3A, 3B, and 3C illustrate various possible hydrocyclones of the present
invention using a helical conduit 305 in the form of a spiral, each having a
suspension
entrance 301 and nozzles 313 for the injection of a fluid or fluids onto the
conduit 305. Each
has an overflow 302 and an underflow 303 connected to an open vessel 312.
Nozzles are
illustrated in the drawings to convey that fluid enters through the wall of
the conduit.
In the case of FIG. 3A the overflow 302 is at the top of the open vessel 312
and the
overflow outlet is operatively connected to an internal vortex finder 304. The
underflow 303
leaves the open vessel tangentially near the bottom of the open vessel 312. In
this case, a
pump 310 is connected to remove the underflow suspension from the open vessel
312 to
create a greater pressure drop through the hydrocyclone circuit or to affect
adequate
underflow velocity for injection into one or more subsequent hydrocyclones or
for disposal
of underflow through a pipeline. This pump may have a variable speed drive to
control the
flow of underflow 303 and hence to control the partition of suspension between
overflow and
underflow for more effective operation of the hydrocyclone open vessel 312 and
the helical
conduit 305.
In the case of FIG. 3B the overflow 302 leaves through the bottom of the open
vessel
312 and is operatively connected to a vortex finder 304 inside the open vessel
312. A
restriction 311 is placed in the underflow 303 outlet to control the partition
of suspension
between overflow and underflow for more effective operation and control of the
hydrocyclone open vessel 312 and the helical conduit 305. In this case, the
restriction 311
may be in the form of a variable controlled constriction that controls the
desired partition of
the hydrocyclone, as to how much of the suspension leaves through the
underflow 303 and
how much leaves through the overflow 302.
In the case of FIG. 3C the open vessel 312 has a conical bottom 306 and an
underflow 303 that leaves through the conical bottom. The overflow 392 leaves
through the
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Jan Kruyer, Thorsby, Alberta, Canada
top and is operatively connected to a vortex finder 304 inside the open vessel
312.
FIG. 3D is a graph showing the rise velocity of a bitumen droplet in a
commercial oil
sand extraction PSV as a function of bitumen droplet diameter when the PSV
suspension
contains a fresh oil sand slurry mixed with fresh water. The bottom curve
shows the rise
velocity of bitumen droplets when caustic soda is not added to the suspension
and the top
curve shows the rise velocity of bitumen droplets when an optimum amount of
caustic soda
is added to disperse the suspension and cause optimum bitumen droplet rise
velocity. This
curve is based on research data published by Laurier L. Schram, a well known
Syncrude
Canada researcher, in May 1989 in the Journal of Canadian Petroleum
Technology. It shows
that the addition of caustic soda to the suspension causes an almost 20 fold
increase in the
droplet rise velocity. However, the commercial addition of caustic soda to oil
sand ore
results in the accumulation of huge amounts of tailings pond sludge that will
not settle in
ponds adjacent to commercial mined oil sands plants. Altogether eliminating
the use of
caustic soda in gravity induced flotation of bitumen froth currently is not an
option since the
required residence time in commercial flotation vessels would be prohibitive.
However,
imposing a centrifugal force field on the oil sand suspension, instead of a
gravity force field,
may well increase the rise velocity of bitumen droplets in a major way and may
thereby
reduce or eliminate the need for caustic soda additions in mined oil sand
bitumen extraction.
This becomes particularly important when recycle water is used in the
extraction, which
recycle water contains enough detergents to disengage bitumen from oil sand
solids and may
not need further caustic soda additions to disperse the oil sand slurry if a
hydrocyclone with
helical conduit is used to impose a centrifugal force field on the oil sand
suspension for
separation by froth flotation.
FIG. 4A illustrates the top view of a hydrocyclone using a helical conduit 404
in the
form of a spiral consisting of sections that are joined by flanges 420.
Suspension enters from
a supply pipe 401 and flows to the inlet 403 of the conduit 404 where an open
vessel 408
where an open vessel splits the suspension into an overflow 407 and an
underflow 406.
Fluid enters the suspension through nozzles 405. For the convenience of
drawing, these
nozzles are shown mounted along the outside lane of the conduit. However, such
nozzles
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Jan Kruyer, Thorsby, Alberta, Canada
may be mounted along the conduit in any direction entering the cross section
of the conduit
404 in any plane. The flanges 420 serve to connect sections of the spiral
conduit 404 but also
may be used for the insertion of restrictions in the path of the conduit. Such
restrictions are
used to mix the suspension within the conduit after the injection of a fluid
from one or more
nozzles. Various types of restrictions are shown in FIGs 4B, 4C and 4D.
In the case of FIG. 4B the restriction is simply a plate 412 inserted between
flanges
411 in which the plate has a hole with a size that is smaller than the
internal size of the
conduit. The resulting restriction causes turbulence in the suspension and
this turbulence
causes mixing of the suspension. Flow lines 420 are shown in these Figures to
provide some
indication of the flow patterns around an obstruction in the conduits. The
described hole in
the plate may be in the form of a circle or it may be in the form of a half
moon. The half
moon may have the same diameter as the internal diameter of the conduit, and
may be in line
with the conduit inside wall along the outside lane, while the straight
section of the half
moon is close to the centre of the flowing suspension, half way between the
outer lane and
the inner lane. Such a half moon restriction is illustrated in FIG. 4E and
will not restrict the
flow of suspension in the outer lane but will cause the suspension of the
inner lane to mix
with the suspension in the outer lane after having passed the half moon
restriction. In the
case of FIG. 4C the restriction is a half moon with an attachment that is
deformed in the
direction of flow of the suspension to provide for mixing of the suspension
but with less
turbulence as compared with the un-deformed half moon of FIG. 4B. In the case
of FIG. 4D
the restriction is contoured in the form of a half ventury. Venturies are
often used to locally
increase the velocity in a conduit with minimal turbulence. In the case of the
half venture of
FIG. 4D, the outside lane is not disturbed but the inside lane suspension is
accelerated,
causing mixing of the inside lane suspension with the outside lane suspension
while
minimizing undesired turbulence in the conduit, as shown by the flow pattern
420.
Porous sections, each enclosed by a pressure chamber for holding fluid, also
may be
inserted between the flanges of FIG. 4 to replace the need for some or all of
the nozzles.
In FIG. 5 the hydrocyclone with helical conduit is used to clean up bitumen
froth
with the use of an aperture oleophilic wall. Suspension enters the helical
conduit at the inlet
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Jan Kruyer, Thorsby, Alberta, Canada
501 of the conduit and enters the open vessel 512 after passing nozzles 513
for fluid injection
in the suspension. The underflow 503 leaves the hydrocyclone open vessel
tangentially at
the bottom.
It should be noted here that the bottom of a hydrocyclone of the present
invention
refers to the opposite end of the open vessel as to where the helical conduit
connects to the
open vessel. Thus the top of an open vessel of the present invention is that
half of the length
of the open vessel where the suspension from a helical conduit enters the open
vessel, and
the bottom of the open vessel is the opposite half of the length of that open
vessel. This
convention is used for describing the hydrocyclones of the present invention,
since these
hydrocyclones may be mounted with their open vessel axes vertical, horizontal
or at an
incline. In cases where the centrifugal force field is very much larger than
the force of
gravity, the force of gravity has little influence on the operation of
hydrocyclones of the
present invention. These hydrocyclones may then be mounted with the open
vessel axis
vertical, horizontal or at an incline, whichever is more suitable for mounting
or connecting
each hydrocyclone. The orientation of these hydrocyclones is a design
consideration that
may be based on the size and density of solids in the suspension and the
strength of the
centrifugal force field in comparison with the strength of the gravitational
force field present
in the flowing suspension.
In the case of FIG. 5 the hydrocyclone is mounted with the open vessel axis
horizontal. The overflow 502 outlet is operatively connected to a vortex
finder 504 and the
overflow enters a central inlet 532 of an agglomerator 530. Agglomerators of
this type are
described in detail in Canadian copending patent application No. 2,647,855
filed 15 January
2009 entitled: "Design of Endless Cable Multiple Wrap Bitumen Extractors ".
Such
agglomerators often are partly filled with oleophilic balls 533 as shown in
the section cut out
of the drum 530 wall. A convenient level of balls inside the drum is shown by
an
immaginary line 534 drawn on the drum end wall. The overflow 502 from the
hydrocyclone
flows into the agglomerator 530 through a central opening 532 that contains a
rotary seal to
prevent suspension to spill out of the drum past the central opening. The
hydrocyclone
overflow 502 contacts the bed of balls 533 and gives up air in the process due
to the
CA 02661579 2009-04-09
Jan Kruyer, Thorsby, Alberta, Canada
kneading action of the bed of balls and this air escapes through the open
apertures 531 of the
drum 530 cylindrical wall along the upper half of the drum. Water and some
solids also are
released from the overflow 502 that has entered the drum 530 due to the
kneading action of
the bed of oleophilic balls that capture bitumen but allow water and some
hydrophilic solids
to escape through the bottom apertures 539 of the drum 530 and through the
apertures of the
oleophilic apertured belt 535 that surrounds the bottom of the drum 530. The
kneading
action of the balls 533 only temporarily holds the bitumen of the overflow 502
until the
amount of bitumen exceeds the holding capacity of the bed of balls, which bed
then releases
the excess bitumen to the oleophilic apertured belt 535 through the drum
apertures 539 along
the bottom right quadrant of the drum 530 of FIG. 5. From there the adhering
bitumen,
which by that time, compared with the hydrocyclone overflow 502, has lost most
of its gas or
air and a portion of its water and hydrophilic solids, is conveyed upward
towards a set of
rollers 538. These rollers are squeeze roller 538, which squeeze the adhering
bitumen from
the apertured oleophilic wall into a receiver 536 for subsequent continuous
removal as the
bitumen product 537 of separation. This bitumen product 537 normally is a
flowing liquid
that contains little or no air and contains a lower water and hydrophilic
solids content than
the overflow 502 from a hydrocyclone. Water and hydrophilic solids removed in
this
manner from the overflow 502 flow through the apertures 539 of the drum and of
the
apertured oleophilic belt into a tailings receiver 540 to become the tailings
541 of oleophilic
separation, which then is the effluent 542 that is discarded.
FIG. 6 is a flow diagram of an apertured oleophilic wall separator operatively
connected with the helical conduit of a hydrocyclone of the present invention
to recover
bitumen from tailings pond sludge by the separator, followed by a preliminary
bitumen
product clean up by the hydrocyclone system. The oleophilic wall separator is
very similar
to the separator of FIG. 5 of copending Canadian Patent Application No.
2,647,855 entitled
"Design of Endless Cable Multiple Wrap Bitumen Extractors " and the
hydrocyclone is very
similar to FIG. 2A of the present invention.
Sludge may have resided in a tailings pond for a long time and during that
time the
bitumen in that sludge tends to be oxidize, resulting in the formation of
acidic components in
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Jan Kruyer, Thorsby, Alberta, Canada
that bitumen. The acidity of bitumen may be measured by titrating bitumen with
a strong
base, such as potassium hydroxide in a solvent such as alcohol. The measured
acidity of the
bitumen sample is then reported as TAN, which means "total acid number".
Bitumen with a
high TAN represents an upgrading and refining problem because its acidity will
corrode
process equipment at elevated temperatures unless special and expensive metals
are used to
prevent such corrosion. Acids or bases may be injected into the suspension in
the conduit to
react with the organic acids and thereby reduce the TAN of the suspension
bitumen. The
bitumen product from sludge also contains solids that may be removed in part
by injecting
one or more depressant reagent fluids through the wall of the helical conduit
into the flowing
suspension. Fluid reagents injected through the conduit wall may include a
strong base, such
as calcium hydroxide, sodium hydroxide, or potassium hydroxide and may also
include
depressants or modifiers. Sodium silicate may be used as an effective
depressant for the
silica surfaces of some sludge fines. Other depressants may be used as well to
remove pyrite
particles, as well as particles of zircon, iron bearing ore particles and
titanium minerals from
the bitumen containing suspension. In some cases the injected fluid may be in
the form of a
suspension, such as, for example, milk of lime.
With reference to FIG. 6, sludge 601 is fed via a distributor 602 to the top
flight 603
of an aperture oleophilic wall separator where aqueous phase passes through
the apertures
and flows into a drum agglomerator 604 with apertured cylindrical wall 605.
Bitumen
captured by the top flight 603 from the sludge 601 is removed by squeeze
rollers 606 and
becomes the primary bitumen product 607. The aqueous phase entering through
the drum
apertures 605 contacts a bed of oleophilic balls 608 which capture additional
bitumen, and
then the bitumen depleted aqueous phase leaves through the drum apertures and
through the
apertures of the bottom flight 609 to become the final tailings of sludge
separation. The
kneading action of the balls in the bed 608 transfers bitumen to the bottom
flight along the
bottom right quadrant 610 of the aperture agglomerator drum 604 and the bottom
flight 609
conveys this bitumen to a second set of squeeze rollers 611 to produce a
secondary bitumen
product 612. The primary bitumen product 607 and the secondary bitumen product
612 are
combined as a combined bitumen product 613 which is pumped by means of a pump
620
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Jan Kruyer, Thorsby, Alberta, Canada
into the entrance of a helical conduit 614 of a hydrocyclone of the present
invention. The
pump is driven by an electric motor (not shown). The hydrocyclone of FIG. 6 is
similar to
the hydrocyclones illustrated in FIG. 2 or FIG. 4. Several aqueous reagents
fluids 615 may
be introduced into the suspension through the conduit wall by means of
apertures or by
nozzles 616 to achieve the desired surface chemistry modification, the desired
neutralizing to
reduce TAN and the desired frothing of bitumen before the suspension separates
into an
underflow and an overflow of the hydrocyclone open vessel. The underflow 617
will
contain water and hydrophilic solids and the overflow 618 will contain bitumen
froth that
with a smaller amount of solids than the amount of solids in the combined
bitumen product
613 pumped into the conduit 614 inlet. When inorganic bases are injected
through the
conduit wall for reacting with organic acids in the combined bitumen product
613 mixture,
the reduced TAN of the overflow 618 froth will make the contained bitumen less
corrosive.
FIG. 7 is a flow diagram of two hydrocyclones in series. Suspension from a
mixing
tank enters the suction inlet 701 of a pump 702 driven by an electric motor
(not shown) and
enters the conduit 703 of the first hydrocylone 704 under pressure. Gas 705
and/or reagent
fluid 706 may be injected into the flowing suspension through the conduit 703
wall. In this
case the open vessel 707 of the first hydrocyclone is provided with a conical
bottom 708
provided with an outlet 709 for underflow 710. In this case the underflow 710
may consist
of coarse solids that need to be removed from the suspension before a more
effective froth
flotation can take place in a second hydrocyclone 714. The overflow from the
first
hydrocyclone then flows into the inlet of the helical conduit 713 of a second,
probably
smaller, hydrocyclone. A vortex finder 711 inside the open vessel 707 is
connected to an
overflow outlet 712 which is connected to the conduit 713 of the second
hydrocyclone 714.
Gas and a variety of reagent fluids may be injected through the conduit 713 if
the second
hydrocyclone into the suspension. Overflow 716 and underflow 717 leaves from
the open
vessel 715 of the second hydrocyclone. Note that the open vessel of the first,
larger
hydrocyclone is mounted with the axis vertical to allow convenient and
unobstructed
removal of coarse and heavy solids through the conical outlet. This is done in
cases where
the first hydrocyclone is very much larger than the second hydrocyclone and
when the
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Jan Kruyer, Thorsby, Alberta, Canada
suspension speed in the swirl path of the large hydrocyclone open vessel is
low. In contrast,
the second hydrocyclone may be much smaller with a suspension speed in the
swirl path of
the small hydrocyclone that is much higher. In that case the hydrocyclone open
vessel may
be mounted with a horizontal axis since the force field of gravity is
negligible in comparison
with the centrifugal force field. Consequently, selecting and designing the
mounting
alignment of hydrocyclones of the present invention is influenced by the ratio
of centrifugal
force field over gravitational force field. The diameter of the open vessel
and the sizes and
densities of the underflow particles have an impact, as well, on the selection
of the most
appropriate mounting of hydrocyclones of the present invention.
Thus, as described, hydrocyclones may be used in series with one or more
apertured
oleophilic walls to efficiently process bitumen containing suspensions; first
to concentrate
the bitumen and oleophilic solids by froth flotation in a centrifugal force
field, using one or
more hydrocylcones of the present invention; and then to remove gas or air and
water and
hydrophilic solids from the final overflow from these hydrocyclones by means
of aperture
oleophilic walls. Alternately, or in addition the hydrocyclones of the present
invention may
be used to process bitumen product from conventional froth flotation or from
and aperture
oleophilic wall. In this manner, oil sand suspensions, and any other
suspensions that contain
bitumen, may be processed quickly and efficiently while producing a good
quality product.
In yet another application of the present invention comminuted minerals may
separated by
froth flotation in a centrifugal force field,
Of course, it is to be understood that the above-described arrangements, and
specific
examples and uses, are only illustrative of the application of the principles
of the present
invention. Furthermore, the inventions described in copending patent
applications of the
present inventor may be combined with the present invention for more effective
processing
of a range of suspensions of many types. 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
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Jan Kruyer, Thorsby, Alberta, Canada
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 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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