Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02813828 2013-04-22
SYSTEM AND INTEGRATED METHOD FOR TREATMENT OF TAILINGS FROM
BITUMEN EXTRACTION PROCESS
FIELD
The present disclosure relates generally to the field of processing of mined
oil sands.
More particularly, the present disclosure relates to the treatment of tailings
from a froth
treatment process that generates tailings. More particularly, the present
disclosure relates to
the treatment of tailings from a paraffinic or a naphthenic froth treatment
process.
BACKGROUND
Oil sands are deposits comprised of bitumen, clay, sand and connate water, and
make up a significant portion of North America's naturally-occurring petroleum
reserves. To
produce a marketable hydrocarbon product from the oil sands, the bitumen must
be
recovered or extracted from the oil sands matrix. Depending on the reserve
type, bitumen
may be recovered by surface mining or in-situ thermal methods, such as steam
assisted
gravity drainage (SAGD), cyclic steam stimulation (CSS), vapor extraction
process (VAPEX),
liquid addition to steam for enhancing recovery (LASER) or derivatives
thereof.
Because the bitumen itself is a tar-like, highly viscous material, separating
it from the
sands poses certain practical difficulties. An example of a common extraction
technique is
known as a water-based extraction process, where hot water, air, and typically
process aides
are added to crushed ore at a basic pH to form a slurry. An oil-rich froth
"floats" or rises
through the slurry as a hydrocarbon phase which can be skimmed off from the
top of a
separation vessel. The result is an extract that typically comprises two
parts: a hydrocarbon
phase known as a bitumen froth stream, made up of bitumen, water and fine
solids, and an
aqueous phase known as extraction tailings, made up of coarse solids, some
fine solids, and
water. The bitumen froth typically comprises bitumen (approximately 60% by
weight), water
(approximately 30% by weight), and solids (approximately 10% by weight), and
must
undergo a froth treatment process to separate the organic content from the
water and solid
contaminants. Due to its high viscosity, the first step is typically the
introduction of a solvent,
usually a hydrocarbon solvent such as naphtha or a paraffinic solvent. This
step is known as
froth separation, and helps to accelerate the separation of solid particles
dispersed within the
1
CA 02813828 2013-04-22
froth by increasing the density differential between the bitumen, water, and
solids as well as
reducing the viscosity of bitumen. Separation is carried out by any number of
methods, such
as centrifugation or gravity separation.
Paraffinic froth treatment is understood to have several advantages over
naphtha-
based treatment, as discussed in Canadian Patent Nos. 2,149,737 and 2,217,300.
One
example of a benefit is the partial rejection of asphaltenes: adding a
paraffinic solvent to
bitumen froth causes some of the asphaltene component of the bitumen extract
to precipitate
from the froth and consolidate with the solid components, such as minerals and
clays. A
further benefit of paraffinic froth treatment is that, as a result of the
adsorption of water
droplets and clays to the hydrophilic sites of the asphaltene molecules, the
final bitumen
product contains only a small amount of emulsified droplets and clay particles
which can be
sources of corrosion and catalyst poisoning. The details of one method of
paraffinic froth
treatment are set out in Canadian Patent No. 2,587,166 to Sury.
The result of the paraffinic froth treatment process is diluted bitumen and a
second
tailings stream, known as froth treatment tailings, made up of water, solids,
and residual
hydrocarbon (solvent, rejected asphaltenes, and un-recovered bitumen) which
undergo
further treatment to prepare the tailings for safe disposal. Dilution water is
added to avoid
foaming within the TSRU (described below) and also the blockage of associated
tubings and
internals The first step in this further treatment is to recover solvent
through any number of
processes known collectively as tailings solvent recovery. Recovered solvent
may then be
reused in the froth separation process. Tailings from a tailings solvent
recovery unit (TSRU),
known as TSRU tailings, are then disposed of. Table 1 sets out an example of
the
composition of TSRU tailings:
2
CA 02813828 2013-04-22
Component Weight Percent
Maltenes 1
Asphaltenes 5
Solvent 0
Fines 6.5
Sands 3.3
Water 84.3
TOTAL: 100
Table 1: TSRU Tailings Composition
The specific properties of the tailings will vary depending on the extraction
method used, but
tailings streams are essentially spent water, asphaltenes, unrecovered
hydrocarbon,
reagents, and waste ore left over once the usable bitumen has been removed.
While effective, the treatment process requires the use of large quantities of
heat,
solvent, and water in the form of steam and process water (dilution water),
which significantly
increases the cost associated with recovery of petroleum from the bitumen-
laden oil sands.
One known method of recovering the water is to simply direct the TSRU tailings
into
reservoirs known as tailings ponds, and allow the solid components to settle
and separate
from the water over time. Residual heat escapes into the atmosphere, while the
tailings water
is retained for future use, with some loss due to evaporation. This method is
not preferred for
at least three reasons. First, a significant amount of time is required for
most of the solid
materials to precipitate out of the tailings by operation of gravity alone.
Secondly, it does not
allow for the recovery of any of the large amount of energy contained within
the tailings
stream in the form of heat. The heat lost is high, as tailings dumped into the
ponds are at
temperatures between 70 C and 90 C. Thirdly, tailings ponds do not readily
permit recovery
of any of the residual hydrocarbon component within the tailings.
Rather than simply disposing of TSRU tailings, it is desirable to recover a
portion of
the usable components of the TSRU tailings stream to reduce the overall cost
of extracting
petroleum resources from oil sands and improve the environmental performance.
The energy
and water recovered can ideally be reused in further steps of the extraction
process or
3
CA 02813828 2016-01-11
recycled to the TSRU to be used as dilution water. This has the advantage of
improving the
overall energy efficiency of the extraction process. It is further desirable
to minimize the volume of
tailings that must be disposed. By removing a certain amount of water from the
tailings, the
streams can be substantially reduced to minerals and unrecovered hydrocarbon.
Several attempts to recover heat, water, and other reagents from tailings
streams are
known. Methods are disclosed in U.S. Patent Nos. 4,343,691, 4,561,965 and
4,240,897, all to
Minkkinen. These patents are directed to heat and water vapor recovery using a
humidification/dehumidification cycle. U.S. Patent No. 6,358,403 to Brown et
al. describes a
vacuum flash process used to recover hydrocarbon solvents from heated tailings
streams. There
has been, however, a lack of success in effective water and energy recovery.
Canadian Patent No. 2,674,660 to Esmaeili et al. is directed to systems and
methods for
treating tailings from bitumen extraction.
SUMMARY
It is an object of the present disclosure to obviate or mitigate at least one
disadvantage of
known systems or methods.
In one aspect, the present disclosure provides a method for treating tailings
from a froth
treatment process, the tailings comprising sand, clay comprising kaolin,
water, and hydrocarbons,
the method including dewatering the tailings comprising a primary water
separation and a
secondary water separation to produce dewatered tailings and recovered water,
the dewatered
tailings having a hydrocarbon content and a solids content to support
combustion of the
dewatered tailings, combusting the hydrocarbons in the dewatered tailings in a
combustion
chamber to cause a dehydration reaction converting kaolin into metakaolin and
to produce fly ash
and bottom ash, recovering calcined fines comprising metakaolin from the fly
ash or from the
bottom ash, or from both the fly ash and the bottom ash, and mixing the fly
ash or the bottom ash
or both, a tailings stream and a chemical modifier including a sodium silicate
solution and caustic
to provide a trafficable deposit.
In an embodiment disclosed, the dewatered tailings have a solids content of at
least 40 wt
percent following the primary water separation. In an embodiment disclosed,
the dewatered
tailings have a solids content of at least 50 wt percent following the
secondary water separation.
In an embodiment disclosed, the dewatered tailings have a solids content of at
least 60 wt
percent following the secondary water separation.
4
CA 02813828 2013-04-22
In an embodiment disclosed, the combustion is carried out at 500 C to 1000 C.
In an
embodiment disclosed, the combustion is carried out at 800 C to 900 C.
In an embodiment disclosed, fine tailings are added to the combustion chamber
to
increase the kaolin content or to control a maximum combustion temperature. In
an
embodiment disclosed, the fine tailings comprise a middling stream, froth
flotation tailings,
paraffinic froth treatment tailings prior to dewatering, naphthenic froth
treatment tailings,
mature fine tailings, or a combination thereof. In an embodiment disclosed,
the fine tailings
stream has been at least partially dewatered or concentrated.
In an embodiment disclosed, water, a substantially hydrocarbon free wet tails,
or a
combination thereof are added to the combustion chamber to control a maximum
combustion
temperature.
In an embodiment disclosed, the combustion is staged to control a maximum
combustion temperature.
In an embodiment disclosed, the combustion chamber comprises a combustion bed
comprising sand and fines. In an embodiment disclosed, the combustion bed
comprises
limestone for in-situ sulfur removal.
In an embodiment disclosed, the combustion chamber is a fluidized bed
combustion
chamber. In an embodiment disclosed, the dewatered tailings are fluidized for
combustion,
with air having an air velocity of between 0.1 m/s and 2.0 m/s. In an
embodiment disclosed,
the air velocity substantially 0.4 m/s.
In an embodiment disclosed, the tailings are tailings solvent recovery unit
(TSRU)
tailings.
In an embodiment disclosed, the bottom ash and bitumen extraction tailings are
combined for solidifying or stabilizing the bitumen extraction tailings.
In an embodiment disclosed, calcined fines comprising metakaolin are recovered
from the bottom ash. In an embodiment disclosed, metakaolin is separated from
the calcined
fines. In an embodiment disclosed, the recovered calcined fines are added to
bitumen
extraction tailings for solidifying or stabilizing the bitumen extraction
tailings. In an
embodiment disclosed, the recovered calcined fines are added to cement,
cementitious
materials or concrete.
CA 02813828 2016-01-11
In an embodiment disclosed, the metakaolin separated from the calcined fines
is added to
bitumen extraction tailings for solidifying or stabilizing the bitumen
extraction tailings. In an
embodiment disclosed, the metakaolin separated from the calcined fines are
added to cement,
cementitious materials or concrete.
In an embodiment disclosed, the fly ash is added to bitumen extraction
tailings for
solidifying or stabilizing the bitumen extraction tailings. In an embodiment
disclosed, the fly ash is
added to cement, cementitious materials or concrete.
In an embodiment disclosed, the calcined fines comprising the metakaolin are
recovered
from the fly ash. In an embodiment disclosed, metakaolin is separated from the
calcined fines.
In an embodiment disclosed, the recovered calcined fines are added to bitumen
extraction tailings for solidifying or stabilizing the bitumen extraction
tailings. In an embodiment
disclosed, the recovered calcined fines are added to cement, cementitious
materials or concrete.
In an embodiment disclosed, the metakaolin separated from the calcined fines
is added to
bitumen extraction tailings for solidifying or stabilizing the bitumen
extraction tailings. In an
embodiment disclosed, the metakaolin separated from the calcined fines is
added to cement,
cementitious materials or concrete.
In an embodiment disclosed, the bitumen extraction tailings comprise mature
fine tailings,
thickened tailings, a middling stream, froth flotation tailings, or coarse
tailings.
In an embodiment disclosed, the fly ash or the bottom ash or both and a
tailings stream
and a chemical modifier are mixed to provide a trafficable deposit.
In an embodiment disclosed, the chemical modifier comprising a sodium silicate
solution.
In an embodiment disclosed, the chemical modifier comprising caustic.
In an embodiment disclosed, the tailings stream is mature fine tailings having
substantially 30 wt% solids content.
In an embodiment disclosed, the tailings are treated according to the recipe:
50 gr of combustion ash, 250 gr of MFT with 30% solid content, 20 gr sodium
silicate
solution, and 2.5 gr dry caustic.
In a further aspect, the present disclosure provides a system for treating
tailings from a
froth treatment process, the tailings comprising sand, clay comprising kaolin,
water, and
hydrocarbons, the system including a dewatering unit comprising a primary
water separation unit
and a secondary water separation unit for removing water from a tailings
stream, producing a
dewatered tailings stream and a tailings water stream, a combustion chamber
for combusting the
dewatered tailings stream, carrying out a chemical reaction whereby kaolin
converts to
6
CA 02813828 2016-01-11
metakaolin to produce fly ash and bottom ash, wherein the combustion chamber
is operated at
800 degrees Celsius and 900 degrees Celsius, a fly ash recovery unit for
recovering calcined
fines comprising metakaolin from the fly ash or a bottom ash recovery unit for
recovering calcined
fines comprising metakaolin from the bottom ash or both a fly ash recovery
unit and a bottom ash
recovery unit, and a mixing unit for mixing the fly ash or the bottom ash or
both with a tailings
stream and a chemical modifier comprising a sodium silicate solution and a
caustic solution to
provide a trafficable deposit.
In an embodiment disclosed, the system includes a metakaolin recovery unit for
recovering metakaolin from the calcined fines.
In an embodiment disclosed, the primary water separation unit provides
thickener
underflow having a solids content of at least 40 wt%. In an embodiment
disclosed, the secondary
water separation unit provides a high solids content stream having a solids
content of at least 50
wt%. In an embodiment disclosed, the high solids content stream comprising
cake. In an
embodiment disclosed, the secondary water separation unit provides cake having
a solids
content of at least 60 wt%.
In an embodiment disclosed, the dewatering unit comprises a thickener unit for
primary
water separation and a centrifuge unit for secondary water separation. In an
embodiment
disclosed, the dewatering unit comprises a thickener unit for primary water
separation and a filter
unit for secondary water separation.
In an embodiment disclosed, the dewatering unit comprises a thickener unit for
primary
water separation and an air drying unit for secondary water separation. In an
embodiment
disclosed, the air drying unit is adapted to deposit the dewatered tailings on
the ground for
moisture release by evaporation to provide dried material. In an embodiment
disclosed, the
combustion chamber adapted to combust the dried material.
In an embodiment disclosed, the thickener unit uses a flocculent, a coagulant,
dilution
water or combinations thereof to flocculate fine particles for removal. In an
embodiment
disclosed, the flocculent and the coagulant are added to the thickener unit at
a single injection
point. In an embodiment disclosed, the flocculent and the coagulant are added
to the thickener
unit at multiple injection points. In an embodiment disclosed, the flocculent
or the coagulant are
added upstream of the thickener unit at one or more locations. In an
embodiment disclosed, the
dilution water is a portion of primary water from the thickener unit.
7
CA 02813828 2013-04-22
In an embodiment disclosed, the dilution water comprises recovered water from
the
dewatering unit.
In an embodiment disclosed, the tailings are tailings solvent recovery unit
tailings.
In an embodiment disclosed, the combustion chamber is operated at between 500
C
to 1000 C. In an embodiment disclosed, the combustion chamber is operated at
between
800 C to 900 C.
In an embodiment disclosed, the combustion chamber is a fluidized bed
combustion
chamber. In an embodiment disclosed, the fluidized bed combustion chamber
comprises a
bed, the bed further comprising material from the dewatered tailings stream,
and inert
products derived from bitumen mining.
In a further aspect, the present disclosure provides a method for treating
tailings from
a froth treatment process to provide a trafficable deposit, comprising mixing
the tailings with
combustion ash and a chemical modifier.
In an embodiment disclosed, the chemical modifier comprising a sodium silicate
solution. In an embodiment disclosed, the chemical modifier comprising
caustic.
In an embodiment disclosed, the tailings comprising mature fine tailings (MFT)
with
substantially a 30 wt% solid content. In an embodiment disclosed, the tailings
comprising
thickened MFT or thickened flotation tails.
In an embodiment disclosed, the tailings are treated according to the recipe:
50 gr of combustion ash, 250 gr MFT with 30 wt% solid content, 20 gr sodium
silicate
solution, and 2.5 gr dry caustic.
In a further aspect, the present disclosure provides a method for treating
TSRU
tailings to provide a trafficable deposit, including receiving a TSRU tailings
stream,
dewatering the TSRU tailings stream to provide cake having at least 50% solid
content,
combusting the cake at between about 800 C and about 900 C, to provide fly ash
and
bottom ash, and mixing the bottom ash or fly ash or both with the tailings to
provide the
trafficable deposit.
In an embodiment disclosed, the tailings comprise MFT.
In an embodiment disclosed, a chemical modifier is mixed with the ash and
tailings. In
an embodiment disclosed, the chemical modifier comprises sodium silicate
solution. In an
embodiment disclosed, the chemical modifier comprises caustic.
8
CA 02813828 2013-04-22
In an embodiment disclosed, the TSRU tailings are treated according to the
recipe:
50 gr combustion ash, 250 gr MFT with 30 wt% solid content, 20 gr sodium
silicate solution,
and 2.5 gr dry caustic.
Other aspects and features of the present disclosure will become apparent to
those
ordinarily skilled in the art upon review of the following description of
specific embodiments in
conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present disclosure will now be described, by way of example
only, with reference to the attached Figures.
Fig. 1 is a flow diagram illustrating an overview of a method of tailings
treatment in
accordance with one disclosed embodiment;
Fig. 2 is a schematic of an example of a tailings treatment system in
accordance with
one disclosed embodiment;
Fig. 3 is a schematic of an example of a tailings treatment system in
accordance with
one disclosed embodiment;
Fig. 4 is a schematic of an example of a dewatering process using a thickener
unit in
accordance with one disclosed embodiment;
Fig. 5 is a schematic of an example of a dewatering process using a thickener
and a
centrifuge in accordance with one disclosed embodiment;
Fig. 6 is a schematic of an example of a dewatering process using a thickener
and a
filter in accordance with one disclosed embodiment;
Fig. 7 is a schematic of an example of a tailings treatment system using a
thickener
and air drying in accordance with one disclosed embodiment;
Fig. 8 is a is a schematic of an example of a process for separating combusted
materials in accordance with one disclosed embodiment;
Fig. 9 is a further example of a process for separating combusted materials in
accordance with one disclosed embodiment; and
Fig. 10 is a schematic of an example of a method of forming a trafficable
deposit in
accordance with one disclosed embodiment.
9
CA 02813828 2013-04-22
DETAILED DESCRIPTION
Generally, in one embodiment, the present disclosure provides a method and
system
for treating TSRU tailings using combustion to recover usable solid components
and steam.
The following description sets out several embodiments of the present
disclosure using the
example of tailings produced from paraffinic froth treatment processes.
However, the
embodiments discussed herein are also applicable to other treatment processes
for bitumen
froth or another industrial application that results in combustible, kaolinite-
bearing tailings.
Flow Diagram
Figure 1 shows a high-level outline of the steps involved in the tailings
treatment
process in accordance with one embodiment of the disclosure. Once froth
separation tailings
undergo tailings solvent recovery processing such as discussed above, they
form a stream of
TSRU tailings 100 comprising water, solid materials, unrecovered hydrocarbons,
and
unrecovered solvent. Dilution water may be added to avoid foaming within the
TSRU and
also to avoid the blockage of associated tubing and internals. In addition,
the TSRU tailings
100 contain a significant amount of heat energy, as they may be released from
a TSRU at a
temperature of approximately 70 C - 93 C, or about 90 C. Owing to the high
specific heat
capacity of water, much of the heat energy of the tailings is stored within
the water portion of
the tailings. As such, both the water and a significant portion of the
enthalpy lost to TSRU
tailings can be extracted from the tailings stream and used in, for example,
other steps in the
oil sands extraction process. Accordingly, one embodiment of the disclosure
provides for a
dewatering unit 110 where recovered hot water 106 is extracted from the TSRU
tailings 100.
In an embodiment disclosed, dewatering 109 includes primary water separation
112
where primary recovered water 114 is extracted from the TRSU tailings 100 to
provide
thickener under-flow (UF) 122, and secondary water separation 116 where
secondary
recovered water 118 is extracted from the thickener underflow 122 to provide
cake 124. The
primary recovered water 114 and the secondary recovered water 118 may be
combined as
recovered hot water 106. The resulting cake 124, or dewatered tailings 115,
are reduced in
both volume and water content, so the following combustion process requires
less heat
energy.
As noted above, the TSRU tailings 100 contain a substantial amount of
hydrocarbons
(e.g. asphaltenes, unrecovered bitumen and solvent). In accordance with one
embodiment
CA 02813828 2014-10-01
disclosed, these hydrocarbons can be used as a source of energy for combustion
once the
TSRU tailings 100 are sufficiently dewatered to provide combustible dewatered
tailings.
Examples of dewatering methods are described below with reference to Figs. 4
to 7. Using
these hydrocarbons may mitigate the environmental challenge of tailings
disposal, since the
amount of solvents and asphaltenes released into the environment can be
significantly
reduced. Accordingly, in one embodiment of the disclosure, dewatered tailings
115 undergo
combustion 128 using the hydrocarbons as a fuel following the dewatering 109.
The
combustion 128 may be more efficient as a result of the dewatering 109, as
dewatered
tailings 115 will combust more readily owing to the removal of recovered hot
water 106. In
an embodiment disclosed the dewatered tailings 115 have a solids content of
greater than
about 50 percent by weight. In an embodiment disclosed, the dewatered tailings
115 have a
solids content of about 60 wt percent. Ammonia, urea, and limestone may be
added to the
combustion 128 for emission control.
As noted above, a constituent element of the solid portion of TSRU tailings is
kaolinite, or solids rich in kaolin. Kaolin, which has a chemical formula of
Al2Si205(0F)4,
undergoes dehydration at temperatures of approximately 500-1000 C to form
metakaolin
according to the following chemical reaction:
2 Al2S1205(OH)4 2 Al2Si207 + 4H20
Accordingly, during combustion 128, the kaolin content of dewatered tailings
115 will
undergo the above dehydration reaction to form metakaolin once the temperature
during
combustion is high enough to reach the activation energy threshold for the
reaction.
Combustion 128 results in two product streams: flue gas 135 and bottom ash
140.
In one embodiment, the metakaolin product of the reaction will form as a fine
solid,
and exit the combustion 128 as a component of flue gas 135. Heavier particles
will settle and
be removed with the bottom ash 140. Flue gas separation 148 is then used to
extract
calcined fines 190, including metakaolin, which has several industrial
applications owing to
their cementitious, or pozzolanic, properties. The remaining components of
flue gas 135 are
then released as low solids flue gas 151 emissions, for example CO, CO2, S0x,
NOx, and
particulates are further treated.
Metakaolin is a well-known supplement for Portland cement; in addition, it is
known to
increase the comprehensive and flexural strengths of cement, and improves the
resistance of
11
CA 02813828 2013-04-22
concrete against corrosive chemicals and freeze-thaw conditions. Similarly,
metakaolin may
be used as a main ingredient of a geopolymer for stabilizing and solidifying
waste streams.
Accordingly, the calcined fines 190 extracted from flue gas 135 or the bottom
ash 140 or both
may be used to treat other tailings streams, such as mature fine tailings
(MFT), coarse
tailings, or another suitable tailings streams resulting from the various
stages of oil sands
extraction processes.
The bottom ash 140 comprises the coarse tailings remnants from the combustion
128, which may include sand, clays (including larger sized meta-kaolinite
particles), minerals,
heavy metal oxides, gypsum, and unreacted limestone. Heavy minerals are
defined herein
as minerals having a specific gravity greater than about 2.85, and including,
without being
limited to, such minerals as rutile, ilmenite, leucoxene, siderite, anatase,
pyrite, zircon,
tourmaline, garnet, magnetite, manzite, kyanite, staurolite, mica, and
chlorite. Among these,
rutile and zircon are considered valuable materials; for example, zircon is
particularly valued
for its applications as an abrasive and an insulator as well as its refractory
properties, while
rutile is used in the preparation of pigments and refractory ceramics. One
embodiment of the
disclosure provides for heavy minerals recovery 170 to extract a portion of
the valuable
constituents of the bottom ash 140. Examples of methods to remove heavy
minerals 175
include gravity, magnetic, and electrostatic separation. De-mineralized bottom
ash 176
comprises the remaining minerals and clay portions left over following heavy
minerals
recovery 170, and may then be disposed of, used for tailings stabilization, or
used for further
separation of gypsum and unreacted limestone.
In an embodiment disclosed, a trafficable deposit 192 may be prepared by
mixing 193
calcined fines 190 or de-mineralized bottom ash 176 from the combustion 128
process or
both and tailings, for example mature fine tailings (MET) 197. In an
embodiment disclosed,
the de-mineralized bottom ash 176 or the calcined fines 190 or both are mixed
194, along
with a chemical modifier 196 to prepare the trafficable deposit 192.
In an embodiment disclosed, the heavy minerals recovery 170 is optional, and
if not
present, the bottom ash 140 could be provided for mixing 193 for preparation
of the
trafficable deposit 192.
Tailings Treatment System
12
CA 02813828 2013-04-22
Figure 2 shows a system in accordance with one disclosed embodiment. TSRU
tailings 200 from bitumen froth treatment processes (for example paraffinic or
naphthenic
froth treatment) enter dewatering unit 210 where a portion of, or much of, the
water in the
TSRU tailings 200 is separated. In an embodiment disclosed, the dewatering
unit 210 may
include primary water separation (PWS) 212 and secondary water separation
(SWS) 216.
Non-limiting examples of suitable dewatering operations methods using a
hydrocyclone,
centrifuge, filters, settling vessels, or thickeners, all with or without the
addition of chemical
aids; however, another process capable of removing water from a TSRU tailings
stream may
function within this embodiment of the disclosure. As a result of the
dewatering, TSRU
tailings 200 have been split into tailings water 205 and dewatered tailings
215. In an
embodiment disclosed, the primary water separation 212 is preferably a
thickener. In an
embodiment disclosed, the secondary water separation 216 is a centrifuge or a
filter. In an
embodiment disclosed, a polymeric flocculant such as Anionic polyacrylamide
(Anionic PAM)
may be used with the option of adding a coagulant. In an embodiment disclosed,
the
coagulant is a polymeric coagulant such as Diallyldimethylammonium Chloride
(DADMAC).
In an embodiment disclosed, the coagulant may be an inorganic coagulant such
as alum,
lime, or gypsum. In an embodiment disclosed, the flocculant is provided in a
dosage range of
about 50 to about 200 ppm. In an embodiment disclosed, the dosage is about 100
ppm. In an
embodiment disclosed, the coagulant is provided in a dosage less than about
200 ppm. In an
embodiment disclosed, the coagulant is DADMAC provided in a dosage about 40
ppm.
The tailings water 205, from primary recovered water 214 and secondary
recovered
water 218, then optionally enters a fines removal unit 220 to recover fine
particulate matter
that may not have been removed by the dewatering unit 210. Non-limiting
examples of fines
removal units include filters, centrifuges, thickeners, clarifiers and
cyclones. Non-limiting
examples of dewatering methods are described further below with reference to
Figs. 4 to 7.
Recovered hot water 206 may then be used in any number of suitable
applications. As noted
above, the TSRU tailings 200 may be released from the TSRU at temperatures of
approximately 90 C, so recovered hot water 206 may leave the fines removal
unit 220 with
enthalpy that may be used in, for example, another step of the oil sands
extraction or
treatment processes or both that require heat energy. Further, the recovered
hot water 206
itself may be reused in other extraction or treatment steps including, but not
limited to, froth
13
CA 02813828 2013-04-22
treatments. The recovered hot water 206 may be recycled to the TSRU to be used
as dilution
water. Any fines 207 recovered by fines removal unit 220 may then be added to
dewatered
tailings 215 and undergo additional treatment along with the solid components
from the
dewatering unit 210 (including primary water separation 212 and secondary
water separation
216).
Dewatered tailings 215 then enter combustion chamber 230. Optionally and
preferably, the combustion chamber 230 is a fluidized bed combustion chamber.
Broadly
speaking, fluidized beds contain solid materials, usually particulate, that
are subjected to
certain conditions to cause them to exhibit the properties and behaviors of a
fluid. In the
fluidized bed combustion in accordance with this embodiment of the disclosure,
solid fuels
(shown as chamber bed 231) are suspended on an upwardly-blowing current of air
234,
causing a tumbling action that mixes gas and solid. In an embodiment
disclosed, air is
provided to provide an upwardly-blowing current of air 234, within the
combustion chamber
230, of between about 0.1 m/s to about 2 m/s. In an embodiment disclosed, the
velocity of
the air 234 is about 0.4 m/s.
In an embodiment disclosed, chamber bed 231 is at least partially made up of
particulate matter from the dewatered tailings themselves. The fluidized bed
combustion
should be operated at a temperature so as to form metakaolin. Limestone,
ammonia and
urea may be added for emission control. In an embodiment disclosed, due to a
high sulfur
content of the fuel, the combustion bed comprises limestone and the fuel is
added, for
example by spraying on to the fluidized bed.
Dewatered tailings 215 contains hydrocarbon molecules such as asphaltenes
rejected during paraffinic froth treatment, unrecovered bitumen and residual
solvent that may
not have been recovered by the TSRU. When ignited, these hydrocarbon
components will
combust within the chamber, releasing heat energy. As one of ordinary skill in
the art will
appreciate, fluidized bed combustion allows for effective reactions and
transfer of heat. The
presence of non-combustible solid material in combustion chamber 230 may not
adversely
affect the combustion process, and the presence of some water within the
boiler feed, which
in this case is dewatered tailings 215, may reduce the combustion temperature
in the
combustion chamber 230 depending on the technology employed. In combustion
processes,
the presence of a certain amount of water moderates the flame or the bed
temperature.
14
CA 02813828 2013-04-22
Advantageously, this may reduce the amount of NOx formed during the combustion
since a
lower combustion temperature reduces the NOx generated from the combustion
air. In an
embodiment, combustion chamber 230 is a modified circulating fluid bed
combustion boiler
where the bed 231 comprises tailings, sand, fines, and other solids added for
control of bed
properties.
According to another embodiment of the disclosure, heat generated during the
combustion operation may be recovered. Water 232, for example boiler feed
water (BFW), is
introduced to, for example, a series of pipes or a compartment within
combustion chamber
230 so that it is in thermal contact with the interior of the combustion
chamber. As the
combustion proceeds, generated heat energy flows into water 232. As a result
of sufficient
heat transfer water 232 will convert to steam 233 and exit combustion chamber
230. Steam
233 may be at any pressure and temperature desired for use as to drive a steam
turbine, as
a heat and/or water source for any other step of the oil sands extraction or
treatment
processes or any other industrial process that may require it.
In some cases, there may be a high sulfur content in the TSRU tailings 200,
particularly in the asphaltene components. As such, a SOx removal step may be
considered
for the design of any combustion process used in accordance with one
embodiment of the
disclosure. In an embodiment disclosed, a limestone bed may be used as part of
a SOx
removal. In an embodiment where both bitumen and asphaltenes are high in
sulfur, this SOx
removal using limestone in the fluidized bed is required. In a non-limiting
example where
combustion chamber 230 is a fluidized bed boiler, the introduction of
limestone in the
fluidized bed is effective for the SOx removal. In one embodiment disclosed,
the presence of
a caustic within the TSRU tailings stream can mitigate a SOx problem, as it is
known that
caustic reacts with SOx. Caustic is known to react with acidic gases like SO2
that will
naturally form in the combustion process as the hydrocarbon in the tailings
contains sulphur.
Moreover, the solid content of TSRU tailings contains materials with similar
molecular
building blocks to that of natural zeolites; they may help to reduce SOx
emissions during the
process.
The combustion proceeds, burning the tailings and converting them to two
streams:
flue gas 235 and bottom ash 240. As discussed above, the kaolin clay component
in the
tailings undergo dehydration synthesis to form metakaolin when the temperature
inside the
CA 02813828 2013-04-22
combustion chamber reaches the 500-1000 C threshold. In one embodiment, fine
tailings
sourced from any stage of the oil sands extraction process (i.e. MFT,
middlings, or flotation
tailings) that produces kaolin-containing fine tailings 229 may be introduced
into combustion
chamber 230. In this manner, additional tailings can be added, thus increasing
the kaolin
content of the tailings in combustion chamber 230 and, consequently, the
production of
metakaolin by dehydration synthesis. Moreover, any residual hydrocarbon in the
fine tailings
will be combusted, recovering useful heat from an otherwise waste product. The
produced
metakaolin as well as other fines, such as illite and smectite will emit from
the combustion
chamber as a portion of flue gas 235 or bottom ash 240. As used herein, fines
are less than
or equal to 44 microns.
It should be noted that the temperature in combustion chamber 230 may exceed
1000 C during combustion. This may have a negative impact on the pozzolanic
properties of
the calcined fines; accordingly, one embodiment of the disclosure provides for
a optimal
design for the combustion for example, by using a staged combustion, primary,
secondary,
tertiary air addition, proper temperature distribution within the chamber can
be achieved and
the length of exposure of the calcined fines to high temperatures can be
reduced, thus
mitigating any damage to the fines. The addition of water, inert or near inert
products (such
as mature fine tailings (MFT) with a low hydrocarbon content) may also be
admitted in
various locations to assist in temperature control or limit in addition to
providing additional
meta-kaolinite production.
In one embodiment, calcined fines 290 contained within flue gas 235 are
separated
by flue gas separation unit 250. Non-limiting examples of appropriate
separation devices
include a cyclone and a bag house filter.
Following separation, flue gas 235 is reduced to low solids flue gas 251,
which may
be made up of the gaseous components released during combustion. In general,
the low
solids flue gas 251 contains a very low solids content, approaching zero, but
may, for
example, include some residual particulate. In a further embodiment, heat
energy contained
in low solids flue gas 251 may be reused in other stages of the oil sands
extraction or
refinement processes or both. For example, low solids flue gas 251 may be used
to dry other
tailings streams such as MFT using a spray dryer. A spray dryer is a type of
dryer in which
the materials to be dried are sprayed to the dryer and the water is removed by
contacting
16
CA 02813828 2014-10-01
with hot air or hot gas. In this case, the hot gas may comprise low solids
flue gas 251. As
noted above, bottom ash 240 comprises sand, gypsum, unreacted lime,
metakaolin, and may
contain valuable heavy minerals. In one embodiment, bottom ash 240 is
introduced into
heavy minerals recovery unit 260 where they are subjected to recovery
operations to retrieve
usable and valuable components from the tailings. Non-limiting examples of
heavy minerals
recovery unit 260 include devices typically used for electrostatic or magnetic
separation
techniques, although another suitable method for extracting heavy minerals
from a coarse or
fine particulate solid or coke may be used in additional embodiments of the
disclosure. The
resulting products from heavy minerals recovery unit 260 include heavy
minerals 262 and de-
mineralized bottom ash 276, which is mainly made up of sand, calcined fines,
gypsum,
unreacted limestone and impurities. De-mineralized bottom ash 276 may then be
disposed of
or used in any appropriate manner.
In an embodiment disclosed, a trafficable deposit 292 may be prepared by
mixing the
bottom ash 240 or the flue gas solids (e.g. calcined fines 290) or both from
the combustion
chamber 230, with tailings, for example mature fine tailings (MFT) 297. In an
embodiment
disclosed, de-mineralized bottom ash 276 or calcined fines 290 or both are
combined with
MFT 297, for example in mixing unit 294, along with a chemical modifier 296 to
prepare the
trafficable deposit 292.
In an embodiment disclosed, the heavy minerals recovery unit 260 is optional,
and if
not present, the bottom ash 240 could be provided to the mixing unit 294 for
preparation of
the trafficable deposit 292.
Tailings Treatment System
Figure 3 shows a system in accordance with one disclosed embodiment.
TSRU tailings 300 are dewatered in dewatering unit 310, comprising primary
water
separation 312 and secondary water separation 316. The primary water
separation 312 at
least partially dewaters the tailings to provide thickener underflow 322 and
primary recovered
water 314. The thickener underflow 322 enters the secondary water separation
316 and is
further dewatered to provide secondary recovered water 318 and cake 324. In an
embodiment disclosed, thickener underflow 322 has a solids content greater
than between
about 30 and 50 weight percent. In an embodiment disclosed, thickener
underflow 322 has a
17
CA 02813828 2014-10-01
solids content greater than about 40 weight percent. In an embodiment
disclosed, thickener
underflow 322 has a solids content of about 45 weight percent.
In an embodiment disclosed, cake 324 has a solids content of greater than
about 50
weight percent. In an embodiment disclosed, cake 324 has a solids content of
greater than
about 60 weight percent.
The primary recovered water 314 and the secondary recovered water 318 may be
used for heat recovery processes or the water itself may be used in other
processes.
The dewatered tailings 315 (i.e. cake 324) enter combustion chamber 330 and
the
hydrocarbon and other combustible components burned to release energy. The
energy may
be used to make steam 333 from water 332. In an embodiment disclosed, a surge
bin or
stock pile of cake may be created or used for storing solids prior to
combustion. This may
separate the production and treating of dry tails from the combustion process.
In an
embodiment disclosed, the combustion chamber 330 operates between about 800 C
and
about 900 C. In an embodiment disclosed, air 334 is supplied for fluidization
in the
combustion chamber 330, for example to a feed distributor, sparger, grid or
other means for
distributing the air 334 across the combustion chamber 330. In an embodiment
the air 334
provides an upward air-current velocity, within the combustion chamber 330, of
about 0.4
m/s. In an embodiment disclosed, limestone 336 is added to the combustion
chamber 330. In
an embodiment disclosed, the dosage of limestone 336 is between about 0 to 5
(molar)
Ca/S. In an embodiment disclosed, the dosage of limestone 336 is about 2.5
(molar) Ca/S. In
an embodiment disclosed, limestone or other materials or chemicals can be
added to reduce
SOx emissions to below regulatory limits. The range is dictated by process
conditions,
limestone particle size, etc. In an embodiment disclosed, the dosage of
limestone 336 of
about 2.5 (molar) can capture between about 90 to 95 percent of SOx emissions.
In an embodiment disclosed, a trafficable deposit 392 may be prepared using
ash
from the combustion process, mixed with tailings, for example MFT 397. Ash,
including fly
ash 355 or bottom ash 340 or both is conveyed to a mixing unit 394 and mixed
with tailings,
such as MFT 397. In an embodiment disclosed, chemical modifiers 396 are added
to
chemically modify the mixture to improve the strength or other material
property of the
trafficable deposit 392. In an embodiment disclosed, the chemical modifier 396
includes
18
CA 02813828 2013-04-22
sodium silicate or caustic or both. The caustic may be provided by dry
caustic, caustic
solution or other sources of caustic known to one skilled in the art.
Figs. 4 to 7 show examples of dewatering and fines removal to prepare the feed
for
the combustion process described herein.
Thickener
Fig. 4 outlines a dewatering method for primary water separation 412 utilizing
a
thickener unit 408.
A flocculent 402 or a coagulant 404 or both are added to TSRU tailings 400 and
this
mixture is added to the thickener unit 408. Primary recovered water 414 is
recovered from
the thickener unit 408, and partially dewatered tailings as thickener
underflow 422 are sent to
secondary water separation 416. A portion of thickener underflow 422 may be
recycled in
order to control the bed height within the thickener unit 408. The portion of
thickener
underflow 422 may be recycled to the thickener unit 408 feed after or before
the chemical
addition. A portion of primary recovered water 414 may be recycled to
thickener unit 408 as
spray 411, or recycled upstream of the thickener unit 408 for mixing with the
flocculent 402,
coagulant 404, and TSRU tailings 400, or recycled both as spray 411 and as
recycle water
upstream of the thickening unit 408.
Thickener and Centrifuge
Fig. 5 outlines a two stage dewatering method utilizing a thickener unit 508
for
primary water separation 512 and a centrifuge unit 542 for secondary water
separation 516.
A flocculent 502 or a coagulant 504 or both may be added to TSRU tailings 500
and
this mixture is added to a thickener unit 508. Primary recovered water 514 is
recovered from
the thickener unit 508, and partially dewatered tailings as thickener
underflow 522 are sent to
secondary water separation 516. A portion of primary recovered water 514 or
secondary
recovered water 518 may be recycled to thickener unit 508 as spray 511, or
upstream of the
thickener unit 508 for mixing with the flocculent 502, coagulant 504, and TSRU
tailings 500,
or recycled both as spray 511 and as recycle water upstream of the thickening
unit 508.
The dewatered tailings, as thickener underflow 522, are received by a
centrifuge unit
542 for secondary water separation 516. In an embodiment disclosed, the
thickener
underflow 522 is a paste with between about 30 to 50 wt percent solids
content. In an
embodiment disclosed, the paste has about 40 to 45 wt percent solids content.
In an
19
CA 02813828 2013-04-22
embodiment disclosed, a portion of the thickener underflow 522 may be recycled
in order to
control the bed height of the thickener unit 508. The portion of thickener
underflow 522 may
be recycled to the thickener unit 508 feed after or before the chemical
addition.
A flocculent 544 or a coagulant 546 or both may be added to thickener
underflow 522
upstream of the centrifuge unit 542.
Secondary recovered water 518 is recovered from the centrifuge 542, and
dewatered
tailings as cake 524 are sent to combustion chamber 530. In an embodiment
disclosed cake
524 has a solids content between 40 and 65 wt%. In an embodiment disclosed
cake 524 has
a solids content of about 55 wt%.
A portion of the primary recovered water 514 or the secondary recovered water
518
may be recycled to centrifuge unit 542, or upstream of the centrifuge unit 542
for mixing with
the flocculent 544, coagulant 546, and TSRU tailings 500, or recycled as
recycle water
upstream of the centrifuge unit 542.
Thickener and Filter
Fig. 6 outlines a two stage dewatering method utilizing a thickener unit 608
for
primary water separation 612 and a filter unit 643 for secondary water
separation 616.
A flocculent 602 or a coagulant 604 or both may be added to TSRU tailings 600
and
this mixture is added to a thickener unit 608. Primary recovered water 614 is
recovered from
the thickener unit 608, and partially dewatered tailings as thickener
underflow 622 are sent to
secondary water separation 616. A portion of primary recovered water 614 may
be recycled
to thickener unit 608 as spray 611, or upstream of the thickener unit 608 for
mixing with the
flocculent 602, coagulant 604, and TSRU tailings 600, or recycled both as
spray 611 and as
recycle water upstream of the thickening unit 608.
The dewatered tailings, as thickener underflow 622, are received by a filter
unit 643
for secondary water separation 616. In an embodiment disclosed, the thickener
underflow
622 is a paste with about 40 wt percent solids content. In an embodiment
disclosed, a portion
of the thickener underflow 622 may be recycled in order to control the bed
height of the
thickener unit 608. The portion of thickener underflow 622 may be recycled to
the thickener
unit 608 feed after or before the chemical addition.
A flocculent 644 or a coagulant 646 or both may be added to thickener
underflow 622
upstream of the filter unit 643.
CA 02813828 2014-10-01
Secondary recovered water 618 is recovered from the filter unit 643, and
dewatered
tailings as cake 624 are sent to combustion chamber 630. In an embodiment
disclosed cake 624
has a solids content between 40 and 70 wt%. In an embodiment disclosed cake
624 has a solids
content of about 60 wt%.
A portion of the secondary recovered water 618 may be recycled to filter unit
643 as
spray 654, or upstream of the filter unit 643 for mixing with the flocculent
644, coagulant 646, and
TSRU tailings 600, or recycled both as spray 654 and as recycle water upstream
of the filter unit
643.
Thickener and Air Dryer
Fig. 7 outlines a two stage dewatering method utilizing a thickener unit 708
for primary
water separation 712 and an air drying unit 726 for secondary water separation
716.
A flocculent 702 or a coagulant 704 or both may be added to TSRU tailings 700
and this
mixture is added to the thickener unit 708. Primary recovered water 714 is
recovered from the
thickener unit 708, and partially dewatered tailings as thickener underflow
722 are sent to
secondary water separation 716. A portion of primary recovered water 714 or
secondary
recovered water 718 may be recycled to thickener unit 708 as spray 711, or
upstream of the
thickener unit 708 for mixing with the flocculent 702, coagulant 704, and TSRU
tailings 700, or
recycled both as spray 711 and as recycle water upstream of the thickening
unit 708.
The dewatered tailings, as thickener underflow 722, are received by the air
drying unit
726 for secondary water separation 716. In an embodiment disclosed, the
thickener underflow
722 is a paste with between about 30 to 50 wt percent solids content. In an
embodiment
disclosed, the paste has about 40 to 45 wt percent solids content. In an
embodiment disclosed, a
portion of the thickener underflow 722 may be recycled in order to control the
bed height of the
thickener unit 708. The portion of thickener underflow 722 may be recycled to
the thickener unit
708 feed after or before the chemical addition.
Secondary recovered water 718 (released water) is recovered from the air
drying unit
726, and dewatered tailings as cake 724 are sent to combustion chamber 730 for
combustion
728. Some water leaves the secondary water separation 716 by water evaporation
717.
Limestone 736 may be added to combustion chamber 730. Air 734 may be added to
combustion
chamber 730. Water 732 may be converted to steam 733 with heat from combustion
chamber
730. Bottom ash 740 exits the combustion chamber 730and mixed with MFT 797 in
mixing unit
794 to provide a trafficable deposit 792. In an embodiment disclosed cake 724
has a solids
content between 70 and 85%. In an embodiment disclosed, cake 724 has a solids
content of
about 80 wt%.
21
CA 02813828 2014-10-01
A portion of the secondary recovered water 718 (released water) may be
recycled to
an extraction or tailings area.
Combustion Products
Fig. 8 is an example outlining the separation of combusted materials. The
dewatered
tailings (such as cake 824) are shown entering the combustion chamber 830.
Limestone,
urea, ammonia and fine tails 829 may also be added. Flue gas 835 is fed to a
flue gas
separation unit 850 from which low solids flue gas 851 flows along with fly
ash 855. The fly
ash 855 is fed to a separation process 863 along with bottom ash 840 exiting
the combustion
chamber 830. In the separation process 863, some of the materials that may be
separated
include heavy minerals and metakaolin (collectively 864) and sand, gypsum,
unreacted
limestone, and impurities (collectively stream 865). Alternately, the bottom
ash 840 may be
treated separately from the fly ash 855.
Combustion Products
Fig. 9 is another example outlining the separation of combusted materials.
Elements
924, 929, 930, 935, 940, 950, 951, 955, 963, 964, and 965 are like elements or
streams with
corresponding numbers in Fig. 8. However, in Fig. 9, a distinct separation
process 966 is
used to separate elements such as heavy minerals and metakaolin (collectively
967) and
sand, gypsum, unreacted limestone, and impurities (collectively stream 968)
from the fly ash
955. Separation process 963 is used to separate such materials from the bottom
ash 940.
Trafficable Deposit
Fig. 10 is an example outlining the preparation of a trafficable deposit using
ash from
the combustion process and tailings, for example mature fine tailings (MFT).
Ash, including fly ash 1055 or bottom ash 1040 or mixtures thereof, is
conveyed to a
mixing unit 1094 and mixed with tailings, such as MFT 1097. In an embodiment
disclosed,
chemical modifiers 1096 are added to chemically modify the mixture to improve
strength of
the trafficable deposit 1092. In an embodiment disclosed, the chemical
modifiers 1096
include sodium silicate or caustic (dry or wet) or both.
In an embodiment disclosed, Table 2 sets out an example recipe which produces
trafficable deposit 1092 having a shear strength of about 10 kPa within about
sixty minutes.
The timeframe indicated includes a cooling or setting of the mixture for about
sixty minutes.
22
CA 02813828 2013-04-22
The ash may be warm or hot from the combustion process or may have cooled to
ambient
temperature.
Component Amount
Combustion Ash 50 gr
MFT 250 gr
with between about 20 and
45 wt% solids content, for
example 30 wt% solids
content
Sodium silicate solution 20 gr
Dry Caustic 2.5 gr
Table 2: Mixture Recipe
Several other advantages of treating tailings streams through combustion in
accordance with embodiments of the present disclosure may include, but are not
limited to:
recovering of hot water from TSRU tailings, eliminating or mitigating the need
to purchase
gas or other fuels for extraction, producing steam for extraction and mining
processes,
eliminating or reducing the volatile organic compound content of emissions
from tailings,
producing usable meta-kaolinite through dehydration synthesis of the kaolinite
content of
TSRU tailings, recovering heavy minerals and/or heavy metal oxides from TSRU
tailings,
reducing the need to store tailings streams in ponds, and reducing the volume
or surface
area of such ponds.
The calcined fines comprising metakaolin and/or the metakaolin produced in the
bottom ash may be used to solidify or stabilize a fine tailings stream (e.g.
mature fine tailings
(MFT)) resulting from bitumen extraction, or as an additive to cement. The
strength of
materials used in tailings pond dykes may be improved with the addition of
meta-kaolinite,
providing benefit in reduced material consumption and more flexible mine
planning. When
added to cement, metakaolin may mitigate an alkaline condition and may provide
a greater
heat resistance. As an example of how metakaolin can be used as an additive to
cement,
Advanced Cement Technologies, LLC (Blaine, WA, USA) markets PowerPozzTM, a
high
23
CA 02813828 2014-10-01
reactivity metakaolin. According to their publicly available data sheet, the
product has been
successfully incorporated into applications for concrete and related products
including high
performance, high strength, and light weight concrete; precast and repetitive
products;
fiberglass products, ferrocement, and glass fiber reinforced concrete; dry
bagged products
such as mortors, stuccos, repair material, and pool plaster; and specialty
uses such as
blended cements, oil well cementing, shotcrete, decorative interior concrete
fixtures, and
sculture.
As used herein, caustic (for example used as a chemical modifier) may include
caustic known to one skilled in the art, including but not limited to dry
caustic, caustic
solution, or combinations thereof.
As used herein, froth treatment process (for example, as a source of tailings)
may
include froth treatment processes known to one skilled in the art, including
but not limited to
paraffinic froth treatment processes, naphthenic froth treatment processes, or
combinations
thereof.
In the preceding description, for purposes of explanation, numerous details
are set
forth in order to provide a thorough understanding of the embodiments.
However, it will be
apparent to one skilled in the art that these specific details are not
required.
The scope of the claims should not be limited by particular embodiments set
forth
herein, but should be construed in a manner consistent with the specification
as a whole.
=
24
