Note: Descriptions are shown in the official language in which they were submitted.
CA 02821783 2013-07-23
OIL SANDS TAILINGS HANDLING SYSTEM AND METHOD
FIELD OF THE INVENTION
The present invention generally related to the field of handling oil sand
tailings and, in particular,
thickened oil sands tailings.
BACKGROUND
Oil sands fine tailings have become a significant environmental issue in
northern Alberta and are the
subject of intense scrutiny from the media and public alike. Oil sand tailings
are generated from
hydrocarbon extraction process operations that separate the valuable
hydrocarbons from oil sand ore. All
current commercial hydrocarbon extraction processes use variations of the
Clark Hot Water Process in
which water is added, and possibly solvents, to the oil sands ore, and
possibly froth, to enable the
separation of the valuable hydrocarbon fraction from the sand and fine
minerals. Once the hydrocarbon
fraction is recovered, the residual water, unrecovered hydrocarbons, solvent
remains, and minerals are
generally referred to as tailings. Conventionally, tailings are transported to
a tailings pond located close to
the oil sands mining and extraction facilities to facilitate pipeline
transportation, discharging, and
management of the tailings. Each tailings pond is contained within a dyke
structure generally constructed
by placing the sand fraction of the tailings within cells or on beaches. In
the tailings pond, the process
water, unrecovered hydrocarbons and minerals settle naturally to form
different strata. The upper stratum
is primarily water that may be recycled as process water to the extraction
process. The lower stratum
contains settled residual hydrocarbon and minerals which are predominately
fines. This lower stratum is
often referred to as "mature fine tailings" (MFT). Mature fine tailings have
very slow consolidation rates
and represent a major challenge to tailings management in the oil sands
industry. Due to the scale of
operations, oil sand tailings ponds cover vast tracts of land and must be
constructed and managed in
accordance with regulations. The management of pond location, filling, level
control, and reclamation is a
complex undertaking given the geographical, technical, regulatory and economic
constraints of oil sands
operations. The composition of mature fine tailings is highly variable. Near
the top of the stratum the
mineral content is about 10 percent weight (wt%) and over time consolidates up
to 50 wt% at the bottom
of the stratum. Overall, mature fine tailings have an average mineral content
of about 30 wt %. While
fines are the dominant particle size fraction in the mineral content, the sand
content may be 15 wt% of the
solids and the clay content may be up to 75 wt% of the solids, reflecting the
oil sand ore and extraction
process. Additional variation may result from the residual hydrocarbon which
may be dispersed in the
minerals or may segregate into mat layers of hydrocarbon. The mature fine
tailings in a pond not only
have a wide variation of compositions distributed from top to bottom of the
pond but there may also be
pockets of different compositions at random locations throughout the pond.
CA 02821783 2013-07-23
Mature fine tailings behave as a fluid-like colloidal material. The fact that
mature fine tailings behave as a
fluid significantly limits options to reclaim tailings ponds. In addition,
mature fine tailings do not behave as
a Newtonian fluid, which makes continuous commercial scale treatments for
dewatering the tailings all the
more challenging. Without dewatering or solidifying the mature fine tailings,
tailings ponds have
increasing economic and environmental implications over time.
There are some methods that have been proposed for disposing of or reclaiming
oil sand tailings by
attempting to solidify or dewater mature fine tailings. If mature fine
tailings can be sufficiently dewatered
so as to convert the waste product into a reclaimed firm terrain, then many of
the problems associated
with this material can be curtailed or completely avoided. As a general
guideline target, achieving a solids
content of 75 wt % for mature fine tailings is considered sufficiently "dried"
for reclamation.
One known method for dewatering MFT involves a freeze-thaw approach. Several
field trials were
conducted at oil sands sites by depositing MFT into small, shallow pits that
were allowed to freeze over
the winter and undergo thawing and evaporative dewatering the following
summer. Scale up of such a
method would require enormous surface areas and would be highly dependent on
weather and season.
Furthermore, other restrictions of this setup were the collection of released
water and precipitation on the
surface of the MFT which discounted the efficacy of the evaporative drying
mechanism. Some other
known methods have attempted to treat MFT with the addition of a chemical to
create a thickened paste
that will solidify or eventually dewater the MFT. One such method, referred to
as "consolidated tailings"
(CT), involves combining mature fine tailings with sand and gypsum. A typical
consolidated tailings
mixture is about 60 wt% mineral (the balance is process water) with a sand to
fines ratio of about 4 to 1,
and 600 to 1000 ppm of gypsum. This combination can result in a non-
segregating mixture when
deposited into the tailings ponds for consolidation. However, the CT method
has a number of drawbacks.
It relies on continuous extraction operations for a supply of sand, gypsum and
process water. The blend
must be tightly controlled.
There are also other technologies which use chemicals to help dewater MFT.
Some added chemicals
have showed thickening of the tailings with no change in solids content by
entrapping water within the
material, which limits the water recovery options from the deposited material.
Some chemical additives
such as gypsum and hydrated lime have generated water runoff that can
adversely impact the process
water reused in the extraction processes or have generated dried tailings with
a high salt content that is
unsuitable for reclamation. The chemical addition technique involves blending
materials in a tank or
thickener apparatus which additionally requires a controlled, homogeneous
mixing of the additive in a
stream of varying composition and flows which then results in inefficiency and
restricts operational
flexibility. Another factor is that many chemical additives can be very
viscous and may exhibit non-
Newtonian fluid behavior. Mature fine tailings, however, particularly at high
mineral or clay concentrations,
also demonstrate non-Newtonian fluid behavior. Still another factor is the
technique of handling the oil
sand tailings after chemical addition. Yet another factor is the technique of
handling or treating the MFT
CA 02821783 2013-07-23
prior to chemical addition. MFT are drawn up by pumps or dredging equipment
from tailings ponds and,
preferably, sent via pipeline to the dewatering treatment area. The thermal
and water performance of oil
sands extraction operations can be greatly improved by using centrifuge,
gravity or cyclone thickeners to
recover warm water from the tailings. The use of thickeners will enable
significant recovery of water and
heat thus allowing more effective water reuse and improved energy efficiency
in the extraction process.
Thickened tailings allows effective disposal of the fine particles, mainly
clays, in a manner that allows
effective land reclamation. Thickeners provide flexibility in handling the
wide range of conditions (flow
rates, solids concentrations, sand to fines ratios) that occur in oil sand
operations. This flexibility is a key
to effective fines management in the oil sands industry. Thickened tailings
(TT) technology has been put
to use at Shell Canada's Athabasca Oil Sands Project. Several other oil sand
operators including Total
E&P Canada, Imperial Oil, and CNRL are considering TT technology in their
upcoming mining projects. In
developing thickened tailings technology, it is important not to overlook the
pipeline transport system
needed to move the tailings from the plant to their final resting area. Once
the water is recovered and
returned to the process, the thickened mixtures are transported in slurry
pipelines to the tailings
management area, often several kilometers away. In comparison with
conventional oil sands tailings,
thickened tailings may have a very high resistance to flow in pipelines. This
resistance is reduced over
time when the thickened tailings are exposed to shear in pumps, pipes, and
other equipment. In 2011,
Total E&P Canada and the Saskatchewan Research Council conducted a study on
the rheological
behavior of thickened oil sands tailings. The flow of thickened oil sand
tailings mixtures was studied using
industrial size equipment. The performance of a large centrifugal slurry pump
was determined and
changes in the mixtures' resistance to flow were measured against the shearing
energy provided by the
pump. When the flow rate is low, the pipeline velocity increases rapidly with
a small increase in the
pressure gradient. This behavior is consistent with the laminar flow of
mixtures with significant yield
stresses. At higher flow rates, an increase in velocity requires an
exponential increase in the pipeline
pressure gradient. This behavior is indicative of a flow dominated by fluid
turbulence. For each of the
mixtures, the transition from laminar to turbulent flow appears to occur at a
velocity of approximately 2.3
m/s. Most slurry pipelines operate in the turbulent flow regime where eddy
mixing forces are available to
keep particles suspended. In a slurry pipeline transporting conventional oil
sand tailings, the sand
particles are carried by a "fluid" composed of clays and other very finely
divided solids dispersed in water.
These carrier fluids are dilute mixtures that tend not to have any significant
yield stress. The turbulent flow
characteristics of conventional slurries allow efficient pumping and
transportation in the tailing disposal
lines. Oil sand thickened tailings are different from conventional slurries.
Their carrier fluids contain
relatively high concentrations of clays and they tend to have significant
yield stresses. Chemicals that are
added to improve the flocculation process tend to augment this yield stress,
sometimes increasing it by
an order of magnitude. In the oil sand slurry, the yield stress augmentation
effect tends to be gradually
reversed during exposure to shear in process equipment. If a mixture has a
relatively high yield stress
then laminar conditions can be expected to persist over the range of
velocities normally associated with
CA 02821783 2013-07-23
slurry pipeline operation. However, there is concern that sand and other
coarse particles will settle out
and accumulate in the pipeline. Even if the mixture has a yield stress that is
sufficient to prevent settling
under quiescent conditions, settling has been observed when the mixture is
exposed to shear in a
pipeline. A significant amount of yield stress reduction occurred when the
thickened tailings were exposed
to shear. It was found that the yield stress of the thickened tailings could
be reduced to half of the original
value by applying a cumulative shearing energy of roughly 1500 kJ per cubic
meter of slurry. There is a
significant disadvantage in that transformation method due to higher energy
consumption and wear on
the pump.
US patent 2013/0043165 A1 by Revington et. al. published February 21, 2013
describes a process for
drying fine tailings with a pipeline reactor system, comprised of providing an
in-line flow of the fine
tailings; continuously introducing a flocculent solution to cause dispersion
and commence flocculation of
the fine tailings and may comprise rapid turbulent mixing; subjecting the fine
tailings to flocculation and
water release conditioning in-line to cause formation and rearrangement of
floes and increasing the yield
shear stress to form flocculated fine tailings while avoiding over-shearing of
the floes; and depositing the
fine tailings to allow the release of water, formation of a non-flowing fine
tailings deposit and drying of the
non-flowing fine tailings deposit. The process enables effective in-line
dispersion, flocculation and water
release, resulting in reliable deposition and drying of the fine tailings
deposit
CA2747886 by WICKES et. al. published January 29, 2013 describes treating a
hydrocarbon-comprising
emulsion with an aqueous component to form an aqueous component-treated
emulsion, and processing
the treated emulsion to recover the hydrocarbon. The aqueous component is
contacted with the
hydrocarbon-comprising emulsion in a manner and proportion so as to promote
coalescence of the like
phases while minimizing shear, which results in a decreased viscosity of the
emulsion and a shift away
from the emulsion inversion region toward a water-continuous state. The
aqueous component-treated
emulsion produced is sufficiently stable to pass through the degasser without
passing through an
emulsion inversion region while being sufficiently unstable to break down into
hydrocarbon and aqueous
constituents during separation downstream of the degasser.
CA2752423 by Kling published on February 1, 2013 provides a method of
processing an oil sands
derived aqueous stream having a concentration of odor causing species such as
hydrogen sulphide. The
method involves monitoring the concentration of the odor causing species in
the oil sands derived
aqueous stream by using an on-line titration, determining a concentration of
an oxidizer such as hydrogen
peroxide to be added to the oil sands derived aqueous stream to oxidize the
odor causing species,
adding the determined concentration of the oxidizer to the oil sands derived
aqueous stream, and
producing a treated aqueous stream depleted in the odor causing species.
CA 02821783 2013-07-23
CA 2789678 by Bara et.al. published on March 16, 2013 describes a process for
flocculating and
dewatering oil sands fine tailings comprising of adding the oil sands fine
tailings as an aqueous slurry to a
stirred tank reactor; adding an effective amount of a polymeric flocculent to
the stirred tank reactor
containing the oil sands fine tailings, operating the reactor at an impeller
tip speed for a period of time that
is sufficient to form a gel-like structure, subjecting the gel-like structure
to shear conditions in the stirred
tank reactor for a period of time sufficient to break down the gel-like
structure to form floes and release
water, and removing the flocculated oil sands fine tailings from the stirred
tank reactor when the maximum
yield stress of the flocculated oil sands fine tailings begins to decline but
before the capillary suction time
of the flocculated oil sands fine tailings begins to substantially increase
from its lowest point.
US patent 3,575,469 by Meyer issued on Apr. 20, 1971 describes the method and
apparatus for
preventing downhill slumping in a shutdown slurry pipeline. Upon shutdown of
the pipeline, a gas is
injected into the line at selected locations to fluidize the solids, thereby
preventing the formation of solid
particle plugs in the low regions of the line and preventing the downward
movement of slurry solids in an
inclined portion of pipeline during a shutdown period and the associated
plugging of the pipeline by said
solids particles. It will enable flow and pressure transmission for re-
suspending the solids upon restart.
US patent 6,344,489 by Spears issued Feb.5, 2002 describes stabilized gas-
enriched and gas
supersaturated liquids, specifically a gas-enriched liquid delivered at a site
of interest that is substantially
bubble free after delivery into a lower pressure liquid or gas environment.
The delivered gas-enriched
liquid is produced by a process comprising the steps of preparing a mixture of
gas and liquid;
compressing the mixture to a pressure such that the gas completely dissolves
in the liquid to form a gas
enriched liquid; enclosing the gas-enriched liquid within a confined space
while retaining substantially the
same pressure. The confined space has at least one dimension less than about
0.2 mm, and has at least
one opening to a liquid or gas environment site of interest having a lower
pressure than that of the
pressure of the confined space; delivering the gas-enriched liquid from the
confined space out through
the at least one exit opening to the lower pressure environment without
formation of bubbles.
US patent 2011/0311321 A1 by Trueman published Dec. 22, 2011 describes a
hydraulic solid
transportation system suitable for the transportation of coal particulates
from a mine, said system
comprising: a pump, a down pipe, at least one hopper, and an up pipe; wherein
said pump pumps fluid
down said down pipe, formation of a particulate-fluid suspension occurs in
said hopper, and by means of
fluid pressure, said fluid purges the particulates from the hopper and along
said up pipe. Said up pipe and
down pipe are connected by at least one cross pipe for inducing a fluid
pressure change in said up pipe.
US patent 2012/0175127 A1 by Yale et.al. published Jul. 12, 2012 describes
methods and systems for
producing a dense oil sand slurry from subsurface reservoirs. The methods
include: reducing pressure at
CA 02821783 2013-07-23
=
a producer pipe inlet to draw a dense slurry into the producer pipe using a
jet pump, generating a diluted
dense slurry using the jet pump, and lifting the diluted dense slurry through
the producer pipe utilizing a
slurry lift apparatus, which may be a fluid lift apparatus. The systems
include: a producer pipe into an oil
sand reservoir, a jet pump configured to generate a low pressure region around
the opening of the
producer pipe to draw the dense slurry into the producer pipe and dilute the
dense slurry to form a diluted
dense slurry, and a gas lift apparatus configured to lift the diluted dense
slurry through the producer pipe
towards the surface of the earth.
US patent 8,276,888 B2 by Osborn et. al. issued Oct. 2, 2012 describes
facilitating dissolution of one or
more gases into a liquid. Preferred gases for use with the described apparatus
are oxygen, air, and
ozone. The apparatus of the present invention comprises a dissolution tank
that includes a pressure
vessel, at least one liquid spray nozzle, and a fluid outlet; a gas source;
means for passing fluid into the
pressure vessel; and a discharge device connected to the fluid outlet, which
is provided with at least one
orifice. Preferred applications include wastewater treatment, treatment of
drinking water, fermentation,
and bioremediation.
US patent 6,848,867 B2 by Kroemmer et. al. issued on Feb.1,2005 describes a
device for introducing
poorly flowing bulk material into a feed line which includes a swirl chamber
connectable to a feed line so
as to form an inlet aperture in a side wall of the swirl chamber. The device
further includes a diffuser plate
through which a loosening fluid may be introduced into the swirl chamber. The
diffuser plate is arranged
in the vicinity of the inlet aperture in the side wall of the swirl chamber. A
device for producing a gas flow
is also provided inside the swirl chamber, the gas flow being directed in the
direction of the inlet aperture.
SUMMARY OF THE INVENTION
The current invention is a method and system for treatment, transportation and
disposal of Tailings, and
in particularly, Thickened Tailings, with the use of gas. The TT include a
higher concentration of solids
and potentially include chemical materials like flocculants that help in the
water recovery during the
thickening process. However, the tailings are complicated to pump due to their
composition and potential
chemical additives, like flocculants, that increase the connections between
the solid particles and hold the
remaining water within the paste. Gas is mixed with the thickened tailings to
reduce its viscosity during
transportation and to enhance the disposal of the tailings by natural drying
or by mixing the tailings with
dry solids, possibly dried tailings. The gas can be air, combustion gas,
natural gas, sour gas, acid gas, or
any other gas mixture available for injection. The mixture of the gas with the
thickened tailings will impact
the thickeners agent and will reduce the viscosity of the TT. The gas bubbles
within the tailings can
reduce the viscosity as well.
CA 02821783 2013-07-23
The thickened tailings that used flocculants are problematic to pump due to
the thickening agent's
behavior. One known option to reduce the TT viscosity in order to allow
pumping is to recycle the tailings
by mechanical pumping to break the chemical strength of the flocculent and to
allow efficient pumping
and disposal on a beach or by any other treatment or disposal means for
tailings disposal. As described
in the prior-art, to reduce the viscosity it is possible to break the
flocculent within the thickened tailings by
recycling the TT on a centrifugal pump before pumping the tailings efficiently
through a pipe line. The
proposed invention is to mix gas, of a controlled amount, with the tailings to
substitute a portion of the
pumping energy required to generate the shear used to increase the pump's
ability with disperse gas
particles that reduce the agglomerate effect of the TT.
The mixed gas breaks into small bubbles within the tailings and physically
reduces the viscosity of the
tailings. In addition, the gas chemical composition can impact the thickening
chemicals, like the
flocculants and polymers chains used for thickening the tailings, and by that
reduce the viscosity of the
tailings. A portion of the gases can react and dissolve into the tailings
while generating a scrubbing effect
and removing contaminates from the gas. The gas that reacted with the
thickened tailings can be
removed and recycled back or used for other processes.
The gas can also reduce the pH of the thickened tailings. This effect depends
on the specific extraction
process in use: the extraction water can include NaOH which increases the
tailings pH where there is a
caustic reaction. The additive chemicals or the thickening process (which can
include centrifuge or
cyclone systems) are effective in the natural tailings slightly caustic pH and
have an impact on the
viscosity. The mixture of the tailings with acid gas can reduce the pH and by
that, reduce the viscosity of
the thickened tailings allowing them to flow better in a pipe line and
possibly release additional water
upon disposal. Any available gas that can reduce the pH can be used, like sour
hydrocarbons, CO2,
combustion or reaction gas, acid gas, SO, or NO, components, Synthetic gas
from a gasifier that includes
sour gas like H2S, etc. The reaction of the thickened tailings with the sour
gas can be apart from the
scrubber system and have a positive environmental impact as it removes
contaminates that will dissolve
and react with components within the tailings.
The invention method includes the following steps:
Mixing oil sands tailings with a thickening agent,
Separating the tailings into solid lean water and thickened tailings,
Mixing the thickened tailings with gas, and
Disposing of the thickened tailings.
The method further includes:
Mixing oil sands tailings with a thickening agent,
Separating the tailings into solid lean water and thickened tailings,
Mixing the thickened tailings with gas,
Mixing the gas-rich thickened tailings with dry solids, and
CA 02821783 2013-07-23
Disposing of the stable tailings mixture.
The method further includes:
Mixing oil sands tailings with a thickening agent,
Separating the tailings into solid lean water and thickened tailings,
Mixing the thickened tailings with gas, and
Pumping the thickened tailings in a pipe system for disposal.
The method further includes:
Adding a chemical thickening agent to a tailings stream,
Pumping the tailings stream and the chemical thickening agent through a pump
while mixing said
thickening agent and the tailings stream, and increasing the fluid pressure in
the pump discharge,
Separating the tailings into solid lean water and thickened tailings,
Adding gas to the thickened tailings stream,
Pumping the thickened tailings stream and a gas through a pump while mixing
said thickened tailings and
said gas and pumping the mixture with the disperse gas within said thickened
tailings through a pipe, and
Disposing of the thickened tailings.
The method further includes:
Adding a chemical thickening agent to a tailings stream,
Recovering water from the thickened tailings,
Adding gas, like air, combustion gas, natural gas, acid gas, or any other
suitable gas, to the thickened
tailings stream,
Mixing the thickened tailings stream with gas to impact the thickening agent's
physical properties and to
reduce the viscosity of the thickened tailings stream,
Separating at least a portion of the added gas, and
Disposing of the thickened tailings.
The method further includes:
Adding a chemical agent to a tailings stream,
Centrifuging the tailings and recovering water,
Adding gas, like natural gas, acid gas or any other suitable gas, to the
thickened tailings stream,
Pumping the thickened tailings stream, and
Disposing of the thickened tailings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention includes the mixture of gas with thickened tailings generated by
an oilsands extraction
facility to reduce the thickened tailings viscosity and improve the
transportability through piping systems
and to improve the water recovery. The mixed gas impacts the selection of the
chemicals that were used
within the extraction process or that were used to enhance the thickening
process. The treated thickened
CA 02821783 2013-07-23
tailings can be pumped to the disposal location and there allow additional
water release and natural or
forced drying of the thickened tailings upon disposal. The invention is
applicable to several thickening
methods, pumping, pipe transportation, and disposal methods.
DETAILED DESCRIPTION OF THE INVENTION
The present invention can be integrated into an extraction facility. A typical
mine oilsands extraction
facility includes water based extraction, possibly with the aid of solvents.
The present processes include
mixing oilsand ore with warm water, possibly with chemicals like NaOH,
solvents, etc. Separation of the
hydrocarbons and some water occurs in a primary separation vessel to generate
a flow of course tailings
(mainly sand and rocks). The coarse tailings flow is directed to the tailings
pond where the coarse tailings
are easily separated into recyclable water and sand that is used in the
tailing pond construction. The
recovered hydrocarbons and froth flow are treated in floatation cells,
possibly with the help of solvents.
The froth treatment typically includes solvents that recovers addition
hydrocarbons and can remove
asphaltin from the bitumen to produce a high quality product. The fine
tailings from the floatation cells and
from the froth treatment facility can be further treated to recover heat and
additional water in a thickening
facility where thickened tailings are generated. The major advantage of the
thickening processes is its
ability to recover additional process water while maintaining the heat energy
within the feed fine tailings.
FIGURE 1 describes a schematic flow diagram of the proposed invention.
Block B includes a thickening facility that includes mixing 3 Fine tailings 1
from the oil sands extraction
facility with chemicals 2 like flocculent that support the water separation.
The mixture 4 is then separated
in a separator 5, that can be any type of commercially available design like
thickener, centrifuge, cyclone
or filter that is capable of separating a portion of the water 6 from the
tailings feed 6 while generating
thickened tailings 7. Thickened tailings 7 are then fed into Block A where
they are mixed 9 with gas 8 and
pumped for further treatment or disposal 11. Mixing of the thickened tailings
with the gas can be
performed prior to the pumping, during the pumping, or after the pumping. The
injected gas pressure for
mixing after the pumping will be higher due the liquid / slurry pressure. The
gas mixed thickened tailings
is further treated in forced heater evaporator / dryer or disposed of on a
sloped shore for further de-
watering, like collecting and recycling the run-off water from the sloped
disposal beach. The thickened
tailings can be further treated by other methods such as by dryer or by mixing
with dry solids to generate
a disposable material. Any other process to treat the fine tailings can be
used as well (such as the use of
cement, gypsum, dry coarse tailings, and so on).
The mixture 9 can be any type of mixture that adds gas 8 to the thickened
tailings 7. This can also be
performed by using a centrifugal pump or any other commercially available pump
where the pumping
energy also mixes the gas with the thickened tailings to reduce their
viscosity.
CA 02821783 2013-07-23
Depending on the extraction process that supplied the fine tailings stream,
the fine tailings 1 can be at a
warm or hot temperature (compared to the temperature of the tailings pond).
The tailings temperature can
vary from 10 C to 95 C for fine tailings from the solvent extraction process.
A portion of the heat supplied
with the tailings is recovered back to the extraction process with the
recovered water 6, and thereby
improving the overall thermal efficiency of the extraction process.
FIGURE 2 describes a schematic diagram with the use of a centrifuge for
recovering water and
generating centrifuge thickened tailings. Oilsands fine tailings 1 are
separated in a centrifuge 5 to recover
water 6 while generating thickened tailings 7. In one option, thickening
chemicals 2 are added 3 to the
fine tailings 1 to improve the centrifuge separation. The recovered water 6 is
recycled back to the
extraction process. In case hot tailings 1 are used, like in the case of
tailings from a Solvents Recovery
Unit (SRU) facility, a portion of the heat within the tailings feed will be
recovered with the recycled water 6
while reducing the overall heat consumption of the Oilsands extraction
process. The thickened tailings 7
are mixed with gas 8. The gas can be air, natural gas, light hydrocarbon gas,
acid gas, CO2, flue gas or
any other type of gas that can reduce the viscosity of the thickened tailings
and improve the water
recovery, like the water run-off when the tailings are disposed of on a slope
reclamation area (not shown).
The gas 8 is injected 9 into the thickened tailings stream 7. The gas may
chemically react with the
chemical component within the thickened tailings and physically reduce the
viscosity of the thickened
tailings. The injected gas can be further mixed into the tailings to generate
and disperse small gas
bubbles into the tailings. This mixing can be done through any commercially
available static mixer or
dynamic mixer,or can also be done by the use of a commercially available pump,
such as a centrifugal
pump. The lowered viscosity tailings flow 10 is pumped through a pipe line for
disposal or further
treatment (not shown)
FIGURE 3 describes a schematic flow diagram with the use of thickener.
Chemicals 2 are added and
mixed 3 into fine tailings flow 1. The fine tailings and the added chemical
flocculants 4 are introduced into
thickener 5. There are several varieties of commercially available chemicals
that can be used for the
thickening process starting from simple gypsum and progressing up to
complicated polymeric thickening
agents. There are also several varieties of commercially available thickener 5
designs that can be used.
The solid lean water from the thickener 6, possibly after further treatment,
is recycled back to the
extraction process. The recycled water 6 temperature reduces the process water
heating requirements as
it is warmer then the recycled water from the tailings pond or from the river.
Gas 8 is added to the
thickened tailings 7 to reduce its flowing viscosity and the thickened
tailings and gas are transferred
through pipe line 10 to disposal 11.
FIGURE 4 describes a schematic flow diagram of the present invention. Fine
tailings 1 can be mixed 3
with chemicals, such as thickening agents 2. The tailings stream 4 is fed into
cyclones 5a and 5B. The
CA 02821783 2013-07-23
cyclones separate the tailings into two streams, an underflow 7 stream with
higher solids concentration
and an over flow stream 6 which contains a solids lean liquid that is recycled
back to the extraction
facility. The separation is completed using commercially available cyclones
that are designed for specified
tailing compositions and flow rates. Figure 4 schematically presents two
cyclones arranged in parallel, 5a
and 5b. Any type of cyclone or multiple arrangements of cyclones can be used
as well as in a typical
commercial cyclone system design where each cyclone is designed to maximize
the required separation
while the overall flow is achieved by using multiple cyclones as required. The
underflow tailings 7 with
higher solids content, also called thickened tailings, is mixed 9 with gas
flow 8. Any commercial mixer 9
that can mix the thickened tailings 7 and gas 8 can be used. The mixed gas
will be selected based on the
actual tailings feed lproperties and the chemicals 2 that were added, if
chemicals were added to the
process to increase the separation in the cyclone 5a and 5b. The mixed
thickened tailings and gas 10 is
separated in separator 11 where a portion of the gas 12 that was introduced to
the system is recovered
and separated from the tailings and then recycled back to be mixed with the
tailings or is separated for
further processing. The thickened tailings can also scrub a portion of the
chemicals within the gas, like
acid gas components and fly solids or liquid particles within gas stream 8, to
generate scrubbed gas
stream 12. The thickened tailings, after a portion of gas 12 is removed and
where a portion of the feed
gas 8 is dissolved, chemically reacted or mechanically captured in the form of
small gas bubbles, are
pumped out 13 for disposal or for further treatment.
FIGURE 5 describes BLOCK A which includes an oil sands extraction facility.
Oilsand ore 1 is processed
with extraction liquid 2 which includes water, possibly with solvents. The
bitumen is separated from the
Oilsands ore and recovered as the process product 6. In this process, a liquid
flow of fine tailings 7 is also
generated. The system and method used in BLOCK A can be any commercially
available process like the
current extraction processes used in Alberta and their future modifications.
Product 6 is the extracted oil.
During the extraction process, non-segregate fine tailings are generated. The
fine tailings can be
generated from the froth treatment process after the course tailings, that
mainly include sand, have been
separated from the process and a portion of the water is recycled back into
the process. BLOCK B
includes the water recovery process which includes separating additional
liquids (mainly water, possibly
with hydrocarbons like solvents) while generating thickened tailings.
Chemicals 8 like flocculants are
added as part of the water recovery process. The water recovery process in
BLOCK B can include a
centrifuge, gravitation thickener or any other water recovery process that can
remove a portion of the
water from the tailings. The thickened tailings flow 10 usually contains
chemicals 8 like flocculants that
were used in recovering water and generating the thickened tailings. The
thickened tailings 10 have a
high viscosity, especially if thickening chemicals, like polymers, were used
in the extraction water
recycling process in BLOCK B. To reduce the thickened tailings viscosity so as
to allow effective pumping
and potentially additional water recovery, Gas 11 is injected into the highly
viscous thickened tailings 10.
The injected gas can be mixed 12 into the tailings flow. The mixture of
tailings and gas 13 is pumped
CA 02821783 2013-07-23
through a commercially available tailings pump 14, like a centrifugal pump,
that further increases the
mixture of the gas and the thickened tailings 15. The gas can be an inert gas
that is not dissolve in the
thickened tailings. Preferably, components within the gas will dissolve into
the thickened tailings and
chemically react with chemicals within the tailings like the flocculants used
for the thickening process. As
the tailings are typically generated using a high pH process that uses soda
caustic, the acid gas will react
with high pH components within the tailings and by that, will reduce the
tailings' viscosity and decrease
the pumping energy requirement for pumping the thickened tailings. In
addition, the pH reduction will
stimulate additional water release with the tailings disposal.
FIGURE 6 describes BLOCK B where thickened oil sands tailings are generated.
There are a few
commercially available technologies, some of which are in commercial use in
oilsand extraction projects,
which generate a thickened tailings flow 2. The thickened tailings flow
usually contains some chemicals,
like flocculants, that were used in recovering water and generating the
thickened tailings. The thickened
tailings have a high viscosity, especially if thickening chemicals, like
polymers, were used in the extraction
water recycling process in BLOCK B. Gas 1 is injected into the highly viscous
thickened tailings. The
injected gas can be mixed 3 into the tailings flow. The mixture of tailings
and gas 4 is pumped through a
commercially available tailings pump 5. The addition of the gas flow to the
tailings is designed to reduce
the viscosity of the thickened tailings and make it suitable for pumping and
then easier for disposal. The
pumped thickened tailings with some gas are pumped 5 through a piping system 6
to a disposal area.
During the disposal process, additional water can be collected or the water
can be evaporated naturally
from the thickened tailings. There are a few methods currently available to
dispose of the thickened
tailings such as disposal on a sloped cell or using any other system to dry
the tailings. The gas
composition and its percentage will be determined according to the particular
system design. With a
caustic based extraction facility and caustic suitable thickening chemicals, a
sour gas or gas that has a
low pH reaction when soluble in water is preferred as it will react with the
thickened tailings to reduce their
viscosity and at the same time, act as a scrubbing medium to scrub the acidity
contaminates within the
gas.
FIGURE 7 includes BLOCK B as described in Figure 6 and generates a thickened
tailings flow 2. The
thickened tailings have a high viscosity, especially if thickening chemicals,
like polymers, were used in the
extraction water recycling process in BLOCK B. Gas 1 is injected into the
highly viscous thickened
tailings. The injected gas can be mixed 3 into the tailings flow. The mixture
of tailings and gas 4 is
pumped through a commercially available tailings centrifugal pump 5 and then
through pipe line 6. To
enhance the mixture and maintain the gas dispersed in the pipe line so as to
prevent separation, an
additional slurry centrifugal pump 7 is added. By adding additional pumps
along the pipe line, each
individual pump energy consumption and head can be reduced. The pumped
thickened tailings slurry
CA 02821783 2013-07-23
viscosity throughout the pipe line system is maintained at a minimum just as
the tailings and the gas is
maintained as a homogenous mixture throughout the pipe line.
FIGURE 8 is similar to Figure 6 where the gas 1 is added to the thickened
tailings 4 after the first
pumping stage. BLOCK B generates flow 2 of thickened tailings. The thickened
tailings are pumped
through a suitable, commercially available pump 5, like a centrifugal pump for
high viscosity and abrasive
fluids. Gas 1 is mixed and dispersed 3 into the pumped flow to reduce the
fluid viscosity for pipe
transportation 6. The gas will be selected based on the thickened tailings
composition and the availability
and cost of different types of gases at the extraction location. The gas
treated thickened tailings is
disposed of at 7. Disposal can be on sloped cells in layers where water can be
collected from the tailings
and natural evaporation can dry the tailings or the gas treated thickened
tailings can be treated with any
other form of treatment for disposal. Additional pumps to overcome the flow
losses within the pipe and to
maintain the flow mixture can be added along the pipe
FIGURE 9 includes BLOCK B which is part of an oilsands extraction facility.
The extraction facility
generates a stream of thickened non-segregated fine tailings 2. A controllable
amount of gas 1 is added
to the thickened flow. The gas feed flow is controlled by the following
parameters:
1. Availability and cost of the proposed gases in the oilsands extraction
facility area.
2. The specific generated oilsands thickened fine tailings that are a
function of the mined ore, the
extraction process, and the thickening process (and especially the thickening
chemicals that are
used in the process)
3. Maximum and minimum range of the gas percentage added to the thickened
oilsands tailings to
prevent separation of the gas and liquids (and possibly the accumulation of
solids in the piping
system).
The gases to be added to the thickened flow can be air, CO2, combustion gas,
synthetic gas generated by
a gasification process, natural gas, produced gas, sour gas, acid gases that
include SOx and NO, or any
mixture of these gases.
The gas 1, in a pre-determined percentage, is added in a controllable way 3
into the thickened fine
tailings flow 2. The mixture of the thickened oilsands 2 with the additional
gas 1 is further mixed in static
mixer 5 to achieve a homogenous mixture and prevent separation of the
components from the thickened
tailings in the pipe. The amount of the gas is determined in such a way as to
minimize the risk of phase
separation within the pipe while reducing the viscosity of the thickened
tailings. Mixture 5 as schematically
described is a static mixture that uses the fluid flow within the pipe for
mixing the gas and the thickened
tailings. Different types of commercially available equipment can be used for
mixing the thickened tailings
and the gas. This includes screw type mixers, planetary mixers, rotating
mixers, Z type mixers, and
CA 02821783 2013-07-23
,
others. Centrifugal pumps can also used as a mixer. The gas treated tailings 6
are transported in piping
system 6 to a disposal location 7 where they are disposed of or treated
further.
FIGURE 10 includes extraction plant BLOCK B combined with a thickening
facility and process recycled
water that generates a flow of high viscosity thickened tailings 2. BLOCK C
includes a combustion gas
source which includes a combustion unit 12 like steam boiler, internal
combustion engine, gas turbine, or
gasifier that can combust carbon or hydrocarbon fuel 16 with oxidizing gas 15
and generates a stream of
combustion gas 13. The combustion gas 13, possibly after further processing,
is compressed 14 and
delivered 1 to the thickened tailings flow 2 where it is mixed at a
controllable rate 3 with the thickened
tailings flow 2. The mixture fluid 4 that contains the thickened tailings 2
and the gas 1 is pumped through
pump 5. A few commercially available designs can be used for pump 5 where the
pumping process acts
also as a mixer for the tailings and the gas to reduce the viscosity of the
mixed fluid in the transportation
pipe 10. A common pump design for pumping the tailings is a centrifugal type
pump 5. The fluid, that
includes a better mixture of the gas 1 and the thickened tailings 2, is pumped
first through pump 5 and
then through pipe line 6. Pipe line 6 can have elbows like 7, 8 and other
fittings that change the flow
direction within the pipe while improving the mixture of the combustion gas 1
and the thickened tailings.
Additional pumps 7 can be located on the line to increase the pressure to
compensate for the losses in
the lines and further enhance mixing of the gas and the thickened tailings, as
described in the other
figures (like Figure 7). The pumped flow 10 also increases the mixture of the
different components (and
phases) with the pumped fluid to maintain a homogenous flow of gas bubbles and
thickened tailings that
include water, clay, as well as other liquids and solids. A portion of the
added gas may dissolve into the
thickened tailings and react with thickening chemicals or other components
within the tailings. The
pumped tailings 10 are disposed of for further water separation, natural
drying on a slope, or for further
treatment like forced drying with combustion heat.
FIGURE 11 includes extraction plant BLOCK B combined with a thickening
facility and process recycled
water that generates a flow of high viscosity thickened tailings 4. BLOCK C
includes a combined power
and combustion gas source that generates mechanical or electrical energy, and
possibly steam, from a
combustion process. A portion of the generated energy and heat can be used in
the extraction facility in
BLOCK B. A carbon based fuel, like natural gas 16, is combusted with oxidizer
gas, like air 15. The
combustion can be part of an internal combustion piston based engine 17 or gas
turbine. The energy
generated from the combustion process can be used, directly or indirectly, for
operating the pumps which
drive the tailings to the tailings pond or to a disposal area, while the
combustion gas can be compressed
and added to the tailings flow. The indirect use of the energy can include the
operation of an electric
generator 25 rotating by engine 17. The tailings pump 5, like a centrifugal
pump, is energy integrated
with a combustion engine 17. The combustion engine combusts fuel 16 with an
oxidizing gas 15 like air
and generates mechanical or electrical energy 22. The generated energy 22 is
used to operate a
CA 02821783 2013-07-23
centrifugal pump 5. A portion of the generated energy 21 is used to compress
19 a portion of the
combustion gas 18 (possibly after cooling it down to a lower temperature) and
adding the compressed
combustion gas 20 to the tailings flow 4 in a controllable amount. The mixture
of the thickened tailings
and combustion gas 6 has a lower viscosity and it is pumped for a disposal
through a piping system 6.
The pumping energy 22 to operate pump 5 is supplied from the combustion
process that operates engine
17. Additional pumps can be installed and aligned the tailings pipe line 6 to
transfer the tailings and
combustion gas mixture for disposal 10.
FIGURE 12 shows BLOCK B that includes the tailings thickening facility.
Oilsands tailings 1 are mixed 3
with a flocculent chemical 2. The tailings and flocculent mixture 4 is then
separated in separator 5, which
can be a gravity based table separator, thickening centrifuge, drum thickeners
or any other type of
commercially available thickening equipment. Process quality water, at a
temperature close to the tailings
feed 1 temperature, is recovered 6 for re-use in the extraction process that
generates the tailings stream
1. The thickened tailings 7, with a higher percentage of solids and higher
viscosity, partially due to the
thickening chemical agent 2 that was used in the thickening process in BLOCK
B, is further treated with
gas 16 to reduce its viscosity and make it more suitable for transportation
through a piping system. Gas 8
is mixed 9 with the thickened tailings 7 in a suitable commercially available
mixer. Depending on the
actual extraction process and the thickening agent 2, the gas can be selected
from the following group:
air, Nitrogen, CO acid gas like CO2, H2S, S0x, NO or caustic reaction gases,
like ammonia gas. Different
gas mixtures can be used as well based on the particular thickened tailings
viscosity reduction, cost, and
site availability. One option is to use the mixture of the gas and the
thickened tailings as means to scrub
gasified chemical components from the gas mixture or fly solids within the
gas. In this case the quantity of
the mixed gas 8 will be higher than the total gas volume absorbed by the
tailings flow 1. The mixture of
the gas and thickened tailings is separated in separator 10 to remove
excessive gas that was not
captured or dissolved into the thickened tailings flow and to maintain the
amount of gas in a controllable
way to prevent separation within the pipe line. The excess removable gas 12
can be directed to a
recycling facility, especially if the gas is expensive or cannot be released
to the environment (like when
caustic and toxic ammonia gas is used or when sour gas (acid gas) is used). A
portion of the scrubbed
gas 17 can be recovered and removed from the system for further treatment orbe
released to the
environment if contaminates were removed in a way that allows the release of
the excess gas 17 to the
environment per regulations. The recycled gas flow 13 is treated in facility
14, which includes a re-
compression unit and possibly other processes like filtration. Make-up gas for
treatment 15 is added to
the recycled gas to replace the gas that reacted or dispersed within the
thickened tailings 7 and the gas
that was removed from the system 17. The recycled gas 16 is recycled back 8
and mixed 9 with the
thickened tailings 7. The gas treated tailings 11 with lower viscosity are
pumped through a pipe line for
disposal or for further treatment.
CA 02821783 2013-07-23
FIGURE 13 shows an oilsands extraction facility at BLOCK B that generates a
stream of thickened
tailings 2. Gas 1 like natural gas, sour gas, CO2, produced gas or other gas
that can react with the
thickened tailings and might include fly solids contaminates, is added 3 to
the thickened tailings 2. The
thickened tailings and the added gas are mixed in mixer 5 to disperse the gas
into the thickened tailings
4. The mixture 6 is separated to remove any excessive scrubbed gas 8. A
portion of the gas is captured
by the thickened tailings 6, as well as solids contaminates that are scrubbed
by the thickened tailings 6.
The treated thickened tailings and the remaining gas that was dissolved or
dispersed in the tailings
stream is pumped 9 through a centrifugal pump for disposal or for further
treatment. The treated
thickened tailings has a lower viscosity and as such, is more suitable for
transportation through piping
systems.
FIGURE 14 shows an oilsands extraction facility BLOCK B which generates a high
viscosity thickened
oilsands tailings flow 2. Gas flow 15, which might include air, combustion
gas, acid gas or other gases
available in the process area, is added to the thickened tailings flow. To
disperse the gas into the tailings,
a mixing apparatus 3 can be used. There are a few commercially available units
that can be used to
enhance the mixture. They can be static apparatuses with internals that
generate the mixture due to the
flow or with the use of internal rotating elements 4 as shown. An internal
rotating element 4 increases
mixing of the tailings 2 and the injected gas 1. This reduces the viscosity of
the thickened fluid as the gas
reacts with the thickening agents within the tailings. In cases where polymers
were used in the thickening
process, the gas or some components within can react with the polymers. The
rotating element can also
transport and pump the mixture 6. The mixture of tailings 6 is pumped by pump
10 where the pumped
fluid has a lower viscosity. BLOCK C includes two potential options that can
be employed separately or
together. One option is to recycle a portion of gas 15, where the portion of
feed gas 15 that was not
dissolved or captured within the thickened tailings stream is separated 12,
recycled back 8 where
additional make-up gas 1 is added 14 and where at least a portion of the
recycled gas 8 and the make-up
gas 1 are combined 14 and recycled back 15 with the tailings. Another option
that can be implemented,
together with the recycled gas or separately, is to also use the mixture 3
with the tailings 2 as a scrubbing
process to remove carry on solids within the mixture stream 15 and other
potential gas contaminates
within the gas stream 15. These can be scrubbed by the thickened tailings 2
during the mixing process 3
and removed from the processed gas 13. The scrubbed gas, after it has reacted
with the tailings 13, is
removed from the system for further use or for disposal.
The two options in BLOCK C can be used together as shown or separately as
described in the text.
