Note: Descriptions are shown in the official language in which they were submitted.
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Enhanced Dewatering of Mining Tailings Employing Chemical Pre-treatment
Background of the Invention
Field of the Invention
The present invention, in one of its aspects, relates to a process for
treating an aqueous slurry
.. such as a tailings stream from a mineral processing operation. Said process
employs a treat-
ment system that includes at least one ionic polymeric de-coagulant and at
least one polymeric
flocculent. In another of its aspects, the present invention also relates to
an aqueous composi-
tion containing an aqueous slurry of particulate material comprising sand
particles and fines
particles and also contains at least one ionic polymeric de-coagulant and at
least one polymeric
flocculent.
Description of the Prior Art
Processes of treating mineral ores, coal or oil sands to extract mineral
values or in the case of
coal and oil sands to recover the hydrocarbons, will normally result in waste
material from the
beneficiation process. Often the waste material is an aqueous slurry or sludge
comprising par-
ticulate mineral material, for instance clay, shale, sand, grit, oil sands
tailings, metal oxides etc.
admixed with water.
Typically, the slurry of waste material would be thickened in one or more
gravity sedimentation
vessels, which are sometimes referred to as thickeners, to concentrate the
solids and recover
some of the water content. In some processes where the valuable metal is
recovered by disso-
lution or leaching, the waste solid material may be separated from the liquor
containing the min-
eral values by a series of counter current sedimentation vessels, sometimes
referred to as a
recovery circuit. In the Bayer alumina process for example, following an
initial digestion stage,
the solids, often referred to as red mud, would be passed to an initial
gravity sedimentation ves-
sel, often referred to as a thickener, and washed in the liquor from
subsequent gravity sedimen-
tation vessels, often referred to as washer vessels. The solids from the
initial thickener stage
would be passed from the base of the vessel as an underflow and into the first
of a series of
counter current sedimentation vessels (washer vessels), in which the solids
from each washer
vessel would be passed as an underflow successively to each subsequent washer
vessel and in
which an aqueous liquor is used to wash the solids in each stage before being
passed to each
previous washer stage and then finally into the first thickener stage.
Polymeric flocculants may
be added into any one or more thickener or water stages to assist with the
solids liquid separa-
tion. The waste solids from the last washer stage would then be passed as an
underflow to a
disposal area, for example a lake or tailings dam.
GB 2080272 describes aqueous suspensions of red mud being removed from the
Bayer pro-
cess for making alumina by the addition of at least the first stage of the
recovery circuit of a
flocculants selected from starch, homopolymers of acrylic acid or acrylates,
copolymers of acryl-
ic acid or acrylates containing at least 80 molar percent acrylic acid or
acrylate monomers and
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combinations thereof and subsequent addition to later, more dilute stages in
the recovery circuit
of a copolymer containing from about 35 to 75 molar percent of acrylic acid or
acrylate and from
about 65 to 25 molar percent of acrylamide monomers.
US 5653946 refers to a process for fluidifying flocculated aqueous suspensions
of red muds in
the production of alumina from bauxite by the Bayer process, which consists:
in dissolving baux-
ite using sodium hydroxide; then, in decanting and in washing the red muds
formed in order to
separate them from the alumina in successive vats, while recycling the washing
water up-
stream; and finally, in eliminating the red muds thus treated; and in which a
flocculant consisting
of a polyacrylamide of molecular weight greater than 10 million is introduced
into the suspen-
sion of one of the successive vats; wherein a dispersing agent formed by an
anionic acrylic acid
polymer of molecular weight lower than 50,000 is added simultaneously with
said flocculant to
the suspension in the same vat.
In a typical mineral, coal or oil sands processing operation, waste solids are
separated from
solids that contain mineral valuables or hydrocarbon in an aqueous process.
The aqueous sus-
pensions of waste solids often contain clays and other minerals and are
usually referred to as
tailings. These solids are often concentrated by a flocculation process in a
gravity thickener to
give a higher density underflow and to recover some of the process water.
In some cases, the waste material such as mine tailings can be conveniently
disposed of in an
underground mine as backfill. Generally, this waste comprises a high
proportion of coarse large
sized particles together with other smaller sized particles and is pumped into
the mine as a slur-
ry, occasionally with the addition of a pozzolan, where it is allowed to
dewater leaving a sedi-
mented solid in place. It is commonplace to use flocculant to assist this
process by flocculating
the fine material to increase the rate of sedimentation. However, in this
instance, the coarse
material will normally sediment at a faster rate than the flocculated fines,
resulting in a hetero-
geneous deposit of coarse and fine solids.
For other applications it may not be possible to dispose of the waste in an
underground mine. In
these cases, it is common practice to dispose of the material, by pumping the
aqueous slurry or
underflow to lagoons, heaps or stacks, which may be above ground, or into open
mine voids, or
even purpose-built dams or containment areas. It is usual to pump the aqueous
slurry to a sur-
face holding area, often referred to as a tailings pit or dam or more usually
a tailings pond in the
case of oil sands. This initial placement of the mining waste into the
disposal area may be as a
free-flowing liquid, thickened paste or the material may be further treated to
remove much of the
water, allowing it to be stacked and handled as a solid-like material. Once
deposited at this sur-
face holding area, water will continue to be released from the aqueous
suspension resulting in
further concentration of the solids over a period of time through the actions
of sedimentation,
drainage and evaporation. Once a sufficient volume of water has been collected
this is usually
pumped back to the mineral or oil sands processing plant.
For example, in the case where the tailings are sent to the disposal area in a
liquid and fluid
form, they must be contained in a lagoon by dams or similar impoundment
structures. The tail-
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ings may have been pretreated by adding flocculating agents and thickened in a
gravity thick-
ener to remove and recover some of the water content, but the overall solids
content is such
that the fluid has no, or a low yield stress, and hence the material behaves
largely as a liquid on
deposition. These lagoons may be relatively shallow, or relatively deep,
depending upon how
much land is available, the location for building impoundment area and other
geotechnical fac-
tors generally within the vicinity of the mine site. Dependent upon the nature
of the solid parti-
cles in the waste, often the particles will gradually settle from the aqueous
slurry and form a
compact bed at the bottom of the deposition area. Released water may be
recovered by pump-
ing or is lost to the atmosphere through evaporation and groundwater through
drainage. It is
desirable to remove the aqueous phase from the tailings whereby the
geotechnical moisture
content is below the liquid limit of tailings solids, in order to manage the
remaining tailings in a
form that has a predominantly solid or semi-solid handling characteristic.
Numerous methods
can be employed to achieve this, the most common, when the material properties
of the tailings
allow, is self-weight consolidation in a tailings dam, whereby the
permeability of tailings is
enough to overcome the filling rate of the dam and water can be freely
released from the tail-
ings. Where the permeability of the tailings is not sufficient for water to
escape freely, polymers
are typically used to improve permeability thereby making the tailings more
suitable for a self-
weight consolidation process. Eventually, it may be possible to rehabilitate
the land containing
the dewatered solids when they are sufficiently dry and compact. However, in
other cases, the
nature of the waste solids will be such that the particles are too fine to
settle completely into a
compact bed, and although the slurry will thicken and become more concentrated
over time, it
will reach a stable equilibrium whereby the material is viscous but still
fluid, making the land
very difficult to rehabilitate. It is known that the flocculants are sometimes
used to treat the tail-
ings before depositing them into the disposal area, to increase the
sedimentation rate and in-
crease the release of water for recovery or evaporation.
In an alternative method, the tailings may be additionally thickened, often by
the treatment with
polymeric agents, such that the yield stress of the material increases so that
the slurry forms
heaps or stacks when it is pumped into the deposition area. Specialised
thickening devices
such as Paste Thickeners or Deep Cone Thickeners may be used to produce an
underflow with
the required properties. Alternatively, the polymeric agents may be added the
tailings slurry dur-
ing the transfer or discharge into the disposal area, to render the material
less mobile and
achieve the required yield stress. This heaped geometry aids more rapid
dewatering and drying
of the material to a solid-like consistency as the water is removed and
recovered more rapidly
through run-off and drainage, and the compaction of the solids may occur more
rapidly through
the increased weight and pressure of the solids when formed into a heap or a
stack. In some
instances, the deposition of the solids is controlled to build up relatively
narrow bands of tailings
which can also dewater quickly through evaporation, prior to adding a new
layer of treated
waste material on top. This is sometimes referred to as thin lift or dry
stacking. Typically, each
relatively narrow band of tailings (i.e. each layer of treated waste material)
would tend to have a
thickness of from 0.1 to 0.5 m. In the case of red mud, this material often
has sufficient yield
stress to form the layered stacks without further polymer treatment and this
method has been
widely used to dispose of tailings from alumina processing for a number of
years. Air drying of
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tailings can be used to great effect where the environment has some
evaporation potential and
there is enough land area to spread the tailings thinly enough for this
process to be effective.
Where the area for evaporation is limited it is possible for the polymers to
be added to the tail-
ings to improve this process. The addition of the polymer may increase the
permeability of the
tailings whereby at least about 20% by weight of water can be allowed to
drain, while another
20% of the water that is typically more associated with the particle surfaces
and the clay matrix
can be removed through evaporation.
It is often useful for the tailings pond or dam to be of limited size to
minimise the impact on the
environment. In addition, providing larger tailings ponds can be expensive due
to the high costs
of earthmoving and the building of containment walls. These ponds tend to have
a gently slop-
ing bottom which allows any water released from the solids to collect in one
area and which can
be pumped back to the plant. A problem that frequently occurs is when the size
of the tailings
pond and the dam are not large enough to cope with the output of tailings from
the mineral pro-
cessing operation. Another problem that frequently occurs is when fine
particles of solids are
carried away with the run-off water. Thus, the released water containing the
fine particles could
have a detrimental impact on recycling and subsequent uses of the water.
Another method for disposal of the mine tailings is to use mechanical
dewatering devices such
as filters and centrifuges. Such mechanical dewatering devices are able to
remove a significant
amount of water from the aqueous minerals slurry, such that the waste material
may be depos-
ited in the disposal area directly with a solid like consistency. In many
cases, it is necessary to
treat the tailings with polymeric flocculating agent immediately prior to the
mechanical dewater-
ing step, to enable this equipment to perform efficiently and achieve the
degree of dewatering
required.
A further method for disposal of the mine waste is through filtration in a
Geotube , whereby the
aqueous slurry placed into a permeable geotextile bag which retains the solids
particles and
some of the water is released by a filtration process, escaping through the
walls of the geotex-
tile bag. In some cases, where the starting permeability of the mine tailings
is low, it may be
desirable to add a flocculating agent in order to increase the filtration rate
and improve the re-
tention of fine solids within the Geotube .
For example, in oil sands mining, the ore is processed to recover the
hydrocarbon fraction, and
the remaining material, constitutes the tailings. In the oil sands extraction
process, the main
process material is water, and the tailings are mostly sand with some silt and
clay, with some
residual bitumen. Physically, the tailings consist of an easily dewatered,
solid part (sand tailings)
and a more fluid part (sludge). The most satisfactory place to dispose of the
tailings, is of course
in the existing excavated hole in the ground. Nevertheless, the sand tailings
alone from the one
cubic foot of ore occupy just about one cubic foot. The amount of sludge is
variable, depending
on the quality and process conditions, but average about 0.3 ft3. The tailings
simply will not fit
into the hole in the ground. Therefore, there is generally a requirement to
build additional im-
poundment areas for the tailings.
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Within the oil sands industry, there are many different types of process
tailings streams as de-
fined in Technical Guide for Fluid Fine Tailings Management, COSIA 2012, which
may require
treatment with polymeric agents. One example is "fine fluid tailings" (FFT)
which is the fines
fraction (mainly silt and clay) from the process after the hydrocarbon content
has been largely
5 recovered, and the sand fraction has been largely removed, usually by
passing the "whole tail-
ings" (WT) through a cyclone. The solids content of the fine fluid tailings
may vary significantly,
depending upon if material has been thickened by gravity sedimentation. Whole
Tailings (WT)
may be regarded as tailings produced from primary or secondary separation
vessels of the ex-
traction plant and contains sand, fines and water. In general, the sand to
fines ratio of the WT
are greater than 4:1 and may be as high as 20:1.
Another example is "composite tails" (CT) in which all the particle size
ranges are present
(sand, silt and clay). This may be the whole tailings, prior to the removal of
the sand, or other
tailings streams which may be formed by subsequent mixing of fine tailings
with sand fractions,
to varying degrees. The sand to fines ratio of CT tend to be greater than 3:1
and may be as
high as 6:1 or 7:1. A further example is "mature fines tailings" (MFT) which
are formed after
storage of fluid fine tailings, or in some cases combine tailings, in a
tailings pond for several
years. FFT tends to have sand to fines ratios significantly below 1:1 and MFT
tend have much
lower sand contents typically less than 0.3:1, for instance less than 0.25:1.
In the oil sands fine tailings pond, the process water, any residual
hydrocarbons and minerals
settle naturally to form different strata. The upper stratum can be
predominantly water that may
be recycled as process water to the extraction process. The lower strata can
contain settled
residual hydrocarbon and minerals which are predominantly fines, usually clay.
It is usual to
refer to this lower stratum as mature fines tailings. It is known that mature
fines tailings consoli-
date extremely slowly and may take many hundreds of years to settle into a
consolidated solid
mass. Consequently, mature fines tailings and the ponds containing them are a
major chal-
lenge to tailings management and the mining industry.
The composition of mature fines tailings tends to be variable. The upper part
of the stratum
may have a mineral content of about 10% by weight but at the bottom of the
stratum the miner-
al content may be as high as 50% by weight. The variation in the solids
content is believed to
be because of the slow settling of the solids and consolidation occurring over
time. The aver-
age mineral content of the MFT tends to be of about 30% by weight. MFT
behaviour is typically
dominated by clay behaviour, with the solids portion of the MFT behaving more
as a plastic-
type material than that of a coarser, more friable sand.
The MFT frequently comprises a mixture of sand, fines and clay. Generally, the
sand is defined
as siliceous particles of any size greater than 44 pm and may be a component
of the MFT sol-
ids in an amount of up to 50% by weight. The remainder of the mineral content
of the MFT
tends to be made up of a mixture of clay and fines (silts). Generally, fines
refer to mineral parti-
cles no greater than 44 pm. The clay may be any material traditionally
referred to as clays by
virtue of its mineralogy and will generally have a particle size of below 2
pm. Typically, the clays
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tend to be a blend of kaolin, illite, chlorite and water swelling clays, such
as smectites which are
sometimes referred to as montmorillonites and may be interlayered with the
other types of clay.
Additional variations in the composition of MFT may be as a result of the
residual hydrocarbon
which may be dispersed in the mineral tailings and may segregate in the
tailings pond into mat
layers of hydrocarbon. The MFT in a pond not only has a wide variation of
compositions distrib-
uted from top to bottom of the pond but there may also be pockets of different
compositions at
random locations throughout the pond.
It has been known to treat aqueous slurry such as tailings using polymer
flocculants. See, for
example, any of:
EP-A-388108;
WO 96/05146;
WO 01/92167;
WO 04/060819;
WO 01/05712; and
W097/06111.
Canadian patent 2,803,904 teaches the use of high molecular weight multi
valent anionic poly-
mers for clay aggregation. Specifically, a polymer comprising an anionic water-
soluble multiva-
lent cation-containing acrylate copolymer is described.
Canadian patent 2,803,025 teaches a polymer similar to the polymer taught in
Canadian patent
2,803,904 with the proviso that the polymer has an intrinsic viscosity of less
than 5 dl/gm.
WO 2017/084986 describes a multivalent cation containing copolymer derived
from one or
more ethylenically unsaturated acids. The copolymer has the following
characteristics: (a) an
intrinsic viscosity of at least about 3 dl/g when measured in 1 M NaCI
solution at 25 C; (b) the
copolymer is derived from a monomer mixture comprising an ethylenically
unsaturated acid and
at least one comonomer, the ethylenically unsaturated acid present in an
amount in the range
of from about 5% to about 65% by weight; and (c) a residual comonomer content
of less than
1000 ppm when the comonomer is an acrylamide. The copolymer, inter-alia, is
useful as a floc-
culent for treating an aqueous slurry comprising particulate material,
preferably tailings from a
mining operation.
US 2018/0201528 describes a method of dewatering an aqueous mineral suspension
compris-
ing introducing into the suspension flocculating system comprising a mixture
of polyethylene
glycol and polyethylene oxide polymers. The mixture of polyethylene glycol and
polyethylene
oxide polymers is said to be useful for the treatment of suspensions of
particulate material, es-
pecially waste mineral slurries and is said to be particularly suitable for
the treatment of tailings
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and other waste material resulting from mineral processing, in particular, the
processing of oil
sands tailings.
Clay-based minerals are known to cause problems in mineral processing
operations. When the
mined ore contains significant amounts of clay, then treatment and disposal of
the waste
(gangue) material after the recovery (beneficiation) of the valuables is often
problematic. This is
because the stacked platelets of a clay mineral particle tend to delaminate
(or break apart)
when contacted with water and these delaminated platelets form (or rearrange
into) network
type structures held together by electrostatic forces between the edges and
the faces of the clay
platelets. The high specific surface area, combined with the hydrophilic
nature of the surfaces,
causes water to become trapped with solids, and the waste is then difficult to
concentrate and
dewater. This can result in both excessive volumes of waste material, soft
deposits which do not
compact readily over time, and loss of process water.
Polymeric flocculants, such as Magnafloc and Rheomax ETD ranges, supplied by
BASF,
have been used to enhance the rate of settling and dewatering of tailings
deposits. However, in
some cases, whilst the polymers do improve the rate and extent of water
removal to some de-
gree, this is not sufficient to increase the solids content of the material
beyond the plastic limit of
the system and, further self-weight compaction does not occur, leading to the
creation of soft
deposits which are not suitable for rehabilitation.
One such example is the Canadian oil sands industry, where it is well
documented that their fine
tailings will remain semi-fluid for many hundreds of years, except where the
process allows for a
significant amount of water evaporation and atmospheric drying. This problem
is especially the
case for deep pour deposits of tailings, which make the most effective use of
land and mining
voids but have limited opportunity for evaporative dewatering. Evaporation to
dewater tailings to
a solids content above the plastic point can only be used on relatively thin
layers of deposited
tailings, which requires a massive area of land to operate effectively.
Another industry which also produces problematic high clay containing tailings
is the phosphate
industry, for example in Florida, USA.
There is a need for a more effective process for dewatering waste solids
containing clays, es-
pecially one that improves upon or overcomes the aforementioned problems.
Summary of the Invention
In accordance with the present invention we provide a process for separating
solids from an
aqueous slurry containing particulate material, which particulate material
comprises sand parti-
cles and fines particles and contains clay particles, which aqueous slurry has
a solids content of
from 25 to 70%, preferably 30 to 70%, by weight and a sand to fines ratio of
from 0.5:1 to 5:1,
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which process comprises applying a treatment system to the aqueous slurry to
cause floccula-
tion of the particulate material, and subsequently separating the so formed
flocculated particu-
late material as solids from the slurry,
in which the treatment system comprises
(a) at least one ionic polymeric de-coagulant which exhibits a weight average
molar mass of
below 2 million g/mol;
(b) at least one polymeric flocculent, which has an intrinsic viscosity of at
least 5 dl/g (meas-
ured at 25 C in 1 M NaCI); and
(c) optionally, at least one cationic coagulant.
By applying a treatment system to the aqueous slurry, the process of the
present invention in-
cludes applying the treatment system, including the components thereof, to any
one or more
components used to form the aqueous slurry. Further, the treatment system may
be applied to
the aqueous slurry by addition of at least one of the treatment system
components to a compo-
nent forming the aqueous slurry and at least one of the treatment system
components to anoth-
er component forming the aqueous slurry. In addition, the treatment system may
be applied to
the aqueous slurry by addition of at least one of the treatment system
components to at least
one component forming the aqueous slurry and the remainder of the treatment
system compo-
nents may be added to the aqueous slurry to be treated according to the
present invention.
Thus, where, for instance, the aqueous slurry is formed by combining any one
or more of whole
tailings (WT), composite tailings (CT), mature fines tailings (MFT), fluid
fines tailings (FFT), thin
fines tailings (TFT) and/or thickened fines tailings (ThFT) together with
other components of the
aqueous slurry such as sand, the treatment system may be applied to any one or
more of these
component streams forming the aqueous slurry or maybe split across different
component
streams or a combination of different component streams and the final aqueous
slurry and dif-
ferent components of the treatment system may be added to different component
streams of the
aqueous slurry.
The invention also relates to a composition formed from an aqueous slurry
containing particu-
late material, which particulate material comprises sand particles and fines
particles and con-
tains clay particles, which aqueous slurry has a solids content of from 25 to
70%, preferably 30
to 70%, by weight and a sand to fines ratio of from 0.5:1 to 5:1,
in which the composition comprises flocculated particulate solids and a
treatment system in
which the treatment system comprises
(a) at least one ionic polymeric de-coagulant, which exhibits a weight average
molar mass of
below 2 million g/mol;
(b) at least one polymeric flocculent, which has an intrinsic viscosity of at
least 5 dl/g (meas-
ured at 25 C in 1 M NaCI); and
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(c) optionally, at least one cationic coagulant
The invention further relates to a treatment system for separating solids from
an aqueous slurry
containing particulate material, which particulate material comprises sand
particles and fines
particles and contains clay particles, which aqueous slurry has a solids
content of from 25 to
70%, preferably 30 to 70%, by weight and a sand fines ratio of 0.5:1 to 5:1,
in which the treatment system comprises
(a) at least one ionic polymeric de-coagulant, which exhibits a weight average
molar mass of
below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at
least 5 dl/g (meas-
ured at 25 C in 1 M NaCI); and
(c) optionally, at least one cationic coagulant.
The invention additionally relates to the use of said treatment system for
separating solids from
an aqueous slurry.
Description of the Drawings
Figure 1 provides a graphical representation of the natural coagulation state
of clays, showing a
plot of suspension (aqueous slurry) viscosity (mPas) versus pH and providing
two-dimensional
representations of the respective coagulated structure of the clay platelets.
Figure 2 illustrates filtration apparatus employed in the test work of the
examples.
Figure 3 is a graphical representation of the results of the filter cake
moisture content variance
on the dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of
Flocculant 1
from Table 1 of Example 1.
Figure 4 is a graphical representation of the results of release of water
solids variance on the
dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of
Flocculant 1 from Ta-
ble 1 of Example 1.
Figure 5 is a graphical representation of the results of the variance of
turbidity of released water
on the dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of
Flocculant 1
from Table 1 of Example 1.
Figure 6 is a graphical representation of the results of the filter cake
moisture content variance
in response to the dose of ionic polymeric de-coagulant Product 1 and
employing 360 g/t Floc-
culant 1 from Table 2 of Example 2.
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Figure 7 is a graphical representation of the results of the release water
solids variance in re-
sponse to the dose of ionic polymeric de-coagulant Product 1 and employing 360
g/t Flocculent
1 from Table 2 of Example 2.
Figure 8 is a graphical representation of the results of the turbidity of
released water variance in
5 response to the dose of ionic polymeric de-coagulant Product 1 and
employing 360 g/t Floccu-
lent 1 from Table 2 of Example 2.
Figure 9 is a graphical representation of the results of the filter cake
moisture content variance
in response to the dose of ionic polymeric de-coagulant Product 1 and
employing 150 g/t Floc-
culent 1 from Table 3 of Example 3.
10 Figure 10 is a graphical representation of the results of the release
water solids variance in re-
sponse to the dose of ionic polymeric de-coagulant Product 1 and employing 150
g/t Flocculent
1 from Table 3 of Example 3.
Figure 11 is a graphical representation of the results of the turbidity of
released water variance
in response to the dose of ionic polymeric de-coagulant Product 1 and
employing 150 g/t Floc-
culant 1 from Table 3 of Example 3.
Figure 12 is a graphical representation of the results of the filter cake
moisture content variance
in response to the dose of ionic polymeric de-coagulant Product 1 and
employing 715 g/t Floc-
culent 3 from Table 6 of Example 6.
Figure 13 is a graphical representation of the results of the turbidity of
released water variance
in response to the dose of ionic polymeric de-coagulant Product 1 and
employing 715 g/t Floc-
culent 1 from Table 6 of Example 6.
Detailed Description
The aqueous slurry should have a solids content of from 25 % to 70% by weight
of the aqueous
slurry. The aqueous slurry to be treated may already have a solids content
within this range.
Typically, however, an aqueous slurry may have undergone some sort of initial
thickening stage
where an amount of the aqueous liquid may have been removed. Such an initial
thickening
stage may, for instance, be a sedimentation stage, such as in a thickening or
sedimentation
vessel or in a pit. Alternatively, the thickening stage may include a belt
thickener or a centrifuge.
Other means of bringing the solids content to within the required range may
also be possible.
By particulate mineral solids we mean that the solids include mineral or
mining solids, typically
from a mining or mineral processing operation. The particulate solids in the
slurry may, for in-
stance, contain filter cake solids or tailings. Often, the particulate mineral
material comprises
tailings. Suitably, the aqueous slurry may comprise phosphate slimes, gold
slimes or wastes
from diamond processing. Typically, the particulate mineral material is
selected from the group
consisting of coal fines tailings, mineral sands tailings, red mud (alumina
Bayer process tail-
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ings), oil sands tailings, mature fines tailings, zinc ore tailings, lead ore
tailings, copper ore tail-
ings, silver ore tailings, uranium ore tailings, nickel ore tailings and iron
ore tailings.
Suitably the at least one ionic polymeric de-coagulant (a) should be added to
the aqueous slurry
before adding the at least one polymeric flocculent (b). Typically, the at
least one ionic polymer-
ic de-coagulant (a) may be added to the aqueous slurry first and subsequently
the at least one
polymeric flocculent (b) should be added. The optional component (c) of the
treatment system,
the at least one cationic coagulant, may be added to the aqueous slurry after
the addition of the
at least one ionic polymeric de-coagulant (a) but before the addition of the
at least one polymer-
ic flocculent (b) or alternatively the optional at least one cationic
coagulant (c) may be added
subsequently to the at least one polymeric flocculent (b). In some cases, it
may even be desira-
ble to add the optional at least one cationic coagulant (c) simultaneously
with the addition of the
at least one polymeric flocculent (b). Suitably, the aqueous slurry employed
in the present in-
vention may comprise clay in a coagulated state and the treatment system
comprises adding to
the aqueous slurry ionic polymeric de-coagulant (a) to reduce the coagulated
state of the clay
particles to a less coagulated state within the aqueous slurry and then
addition of the polymeric
flocculent (b) to flocculate the sand and de-coagulate treated clay particles.
By clay being in a coagulated state, we mean that clay platelets are linked to
each other, typi-
cally by electrostatic forces on the platelet faces and/or edges. Clays may
exist in a number of
coagulated states and typically these include arrangements where the platelets
are linked in a
face-to-face structure; a mixture of face-to-face and edge to face structures;
a mixture of edge
to face and edge-to-edge structures; and edge-to-edge structures. When the
clay is in a sub-
stantially un-coagulated form the clay platelets tend to be substantially
separated. Aqueous slur-
ries tend to exhibit highest viscosity when the clay platelets contain edge to
face structures, for
instance mixtures of edge to face and edge-to-edge structures and especially
mixtures of edge
to face and edge-to-edge structures. This is illustrated in Figure 1.
Those aqueous slurries which contain clay in a coagulated form, particularly
where the coagu-
lated structure induces high viscosities, for instance as understood often to
be the case when
the slurries are oil sands MFT slurries or oil sands FFT slurries, tend to be
particularly difficult to
dewater.
The inventors realised that by employing a treatment system that includes an
ionic polymeric
de-coagulant as part of the treatment system in conjunction with a polymeric
flocculent for clay
containing aqueous slurries, more effective dewatering can be achieved.
Without being limited
to theory, the inventors believe that the effectiveness of the present process
involving the spe-
cial treatment system may be as a result of breaking down the electrostatic
forces between co-
agulated clay platelets so as to allow the polymer chains of the flocculent to
attach to a greater
proportion of the suspended solids without interference from the coagulated
clay. This allows for
the improved release of water which would have been otherwise trapped inside
of the coagulat-
ed clay structures. The inventors believe that the de-coagulant is acting on
the coagulated clay
particles by breaking down or diminishing electrostatic attractive forces
between them and
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hence transferring the clay particles into a form of fully and/or partially
separated particles (as
depicted in Figure 1). Thus, by de-coagulant we mean a chemical additive which
reduces elec-
trostatic attractive forces between coagulated clay particles to render the
particles fully and/or
partially separated. In addition, the inventors have found that the employment
of the treatment
system facilitates the co-disposal of the fines and the sand. Desirably, this
treatment enables
the deposited solids separated from the aqueous slurry to contain both the
fines and sand parti-
cles forming a relatively homogenous deposit with minimal segregation of fines
and sand parti-
cles. Prevention of segregation during co-disposal of the fines and sand
particles is important
because otherwise the heavier sand particles would tend to settle faster while
the fines would
take longer to settle and would tend to be washed away with the liquid
separated from the slur-
ry. Thus, in the process according to the invention the liquid separated from
the aqueous slurry
tends to have a lower fines particles content. This can be measured by well-
known filtration
techniques. Suitably, the liquid separated from the aqueous slurry should have
a solids content
of less than 5% by weight of the total separated liquid. Preferably the solids
content is less than
2% by weight of the total separated liquid, more preferably less than 1% by
weight of the total
separated liquid, even more preferably from 0.001% to 0.75% by total weight of
the separated
liquid, still more preferably from 0.01% to 0.5% by total weight of the
separated liquid, often
from 0.01% to 0.1% by total weight of separated liquid.
The particulate material contained in the aqueous slurry includes sand and
fines. By sand we
mean mineral solids (excluding gravel) with a particle size greater than 44 pm
and generally
less than 2 mm (not including bitumen). By fines we mean mineral solids, such
as silts, with a
particle size of equal to or less than 44 pm (not including bitumen). In
general, the clay compo-
nent of the aqueous slurry is part of the fines component. Thus, fines include
the clay compo-
nent as well as any other non-clayey mineral particles of the aforementioned
size range. The
particulate solid material contained in the aqueous slurry usually comprises a
sand to fines ratio
of from 1:1 to 5:1. Often the sand to fines ratio may be from 1:1 to 4:1, such
as from 2:1 to 3:1.
The aqueous slurry may have a fines solids content of from 10% to 45%, by
total weight of the
aqueous slurry.
The invention is of particular applicability where the aqueous slurry is
derived from an oil sands
fluid fines tailings (FFT), thickened fine tailings (ThFT) or a mature fines
tailings (MFT). Fluid
fine tailings (FFT) are generally understood to mean a liquid suspension of
oil sands fine tailings
or fines dominated tailings in water, with a solids content greater than 2%
but less than the sol-
ids content corresponding to the Liquid Limit. Mature fines tailings are
understood to be a more
specific category of fluid fine tailings with a sand to fines ratio of less
than 0.3 and a solids con-
tent typically greater than 30%. Thin fine tails (TFT) may be understood to be
a category of fluid
fine tailings with a sand to fines ratio of less than 0.3 and a solids content
typically between 15
and 30%. Thickened fine tailings (ThFT) mean fluid fine tailings (FFT) or thin
fine tailings (TFT)
that have been thickened by removal of some of the aqueous content. However,
the solids con-
tent of such thickened fine tailings would not be above the liquid limit and
therefore remain fluid.
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Typically, the aqueous slurry comprises from 10% to 70% clay particles based
on the total
weight of solids. In general, the clay particles tend to be predominantly
kaolinite and illite. The
clay frequently also contains smectite and chlorite. The proportions of the
clay components of
oil sands clays in marine deposits tend to vary according to depth within the
deposit. Generally,
illite species slightly dominates in the top end of the deposits. The smectite
species are general-
ly interlayered with either the kaolinite or illite species, and this tends to
induce additional sepa-
ration of particles.
The at least one ionic polymeric de-coagulant (a) suitably may include water-
soluble polymers
exhibiting a weight average molar mass of below 1.5 million g/mol, for
instance below 1 million
g/mol, such as below 500,000 g/mol or below 100,000 g/mol. In general, the at
least one ionic
polymeric de-coagulant would tend to have a lower weight average molar mass,
typically up to
50,000 g/mol. Desirably, the weight average molar mass of the at least one
ionic polymeric de-
coagulant may tend to be in the range of from 500 to 50,000 g/mol, for
instance from 1000 to
40,000 g/mol, such as 2000 to 30,000 g/mol, or 3000 to 20,000 g/mol.
The at least one ionic polymeric de-coagulant (a) may typically be a
combination of different
ionic polymeric de-coagulants each having a weight average molar mass of below
1 million
g/mol or any of the more precise ranges of molar mass referred to herein.
The at least one ionic polymeric de-coagulant (a) may be cationic, anionic,
amphoteric or zwit-
terionic. In the context of the present invention cationic means that the
ionic polymeric de-
coagulant (a) carries positive charges, anionic means that the ionic polymeric
de-coagulant (a)
carries negative charges and amphoteric means that the ionic polymeric de-
coagulant (a) car-
ries both positive and negative charges. By zwitterionic we mean that the
ionic polymeric de-
coagulant (a) contains positive and negative charges carried on the same
repeating monomeric
units. Preferably, however, the at least one ionic polymeric de-coagulant (a)
is anionic.
Typical polymers which may be used as the ionic polymeric de-coagulant (a)
include
poly(naphthalene sulphonate), prepared for instance by reacting formaldehyde
and naphthalene
sulphonate. Other possible ionic polymeric de-coagulants include polymers
based on melamine
sulphonates and acetone/formaldehyde sulphonates. Generally, these materials
may be pre-
pared by a condensation reaction. Suitable polymers of this category may be
those described in
US 4725665 and US 3277162 which disclose the synthesis of naphthalene
sulphonic ac-
id/formaldehyde condensates starting from naphthalene, sulphuric acid and
formaldehyde. In
the synthesis naphthalene is initially reacted with concentrated sulphuric
acid to form naphtha-
lene sulphonic acid which is reacted with formaldehyde in a polycondensation
reaction and then
finally neutralisation utilising a suitable base, such as sodium hydroxide or
calcium hydroxide.
The use for improving the flowability of inorganic binders like cement and as
fluid (water) loss
additives in cements for oil wells, respectively, is described. Suitable
polymers based on mela-
mine sulphonates are described in US 6555683. This document describes the
preparation of
the polycondensate based on melamine sulphonates and their use to liquefy
inorganic binder
suspensions. These may be synthesised by reacting melamine with formaldehyde
and a sul-
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phite at alkaline pH followed by a polycondensation reaction at acidic pH and
finally neutralising
the polymer with sodium hydroxide. Suitable polymers based on acetone,
formaldehyde sul-
phonate condensates are described in US 4818288 and US 4657593 which describe
such con-
densates for use as dispersants for inorganic binders and US 4657593 describes
the use of
these compounds as dispersion agents for kaolin and clay suspensions. The
condensates are
produced by reacting acetone and sodium sulphite with formaldehyde in a
polycondensation
reaction to give directly the desired polycondensate.
Preferably, however, the ionic polymeric de-coagulant (a) is a water-soluble
polymer derived
from ethylenically unsaturated monomers. One preferred category of water-
soluble polymers
includes those polymers prepared from one or more ethylenically unsaturated
acid monomers
or salts thereof. These polymers may be homopolymers of the one or more
ethylenically unsatu-
rated acid monomers (or salts thereof) or they may be copolymers of said one
or more ethyleni-
cally unsaturated acid monomers (or salts thereof) and one or more
ethylenically unsaturated
non-ionic monomers. Typically, these ethylenically unsaturated non-ionic
monomers may be
selected from the group consisting of acrylamide, methacrylamide, hydroxy
alkyl acrylate, vinyl
acetate, vinyl alcohol, vinyl alkyl ether, allyl alkyl ether, styrene and 01-8
alkyl acrylates.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of
hydroxyethyl
acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable
hydroxyalkyl methacry-
lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and
hydroxybutyl methac-
rylate.
Suitable 01_8 alkyl acrylates as non-ionic comonomers may include methyl
acrylate, ethyl acry-
late, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl
acrylate, isobutyl acrylate,
tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or cyclohexyl
acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl
ether, ally! ethyl
ether, allyl n-propyl ether or allyl isopropyl ether.
The ethylenically unsaturated acid monomers for preparing the aforesaid
homopolymers or co-
polymers as the ionic polymeric de-coagulant (a), may be any suitable
ethylenically unsaturated
monomer bearing an acid group. Suitable acid groups may include carboxylic
acids, sulphonic
acids, sulphuric acids, phosphoric acids or phosphonic acids. By referring to
the specific eth-
ylenically unsaturated acid monomers we also include the corresponding salts
thereof by this
definition. We also include the corresponding anhydride of an acid group in
the definition of eth-
ylenically unsaturated acid monomers. Suitable monomers in this category
include acrylic acid,
methacrylic acid, maleic acid, fumaric acid, itaconic acid, ethacrylic acid,
crotonic acid, mono
esters of ethylenically unsaturated dicarboxylic acids, such as mono methyl
maleate, mono me-
thyl fumarate, mono ethyl maleate, mono n butyl maleate, and mono n butyl
fumarate, styrene
carboxylic acids, maleic anhydride, itaconic anhydride, 2-acrylamido-2-
methylpropylene acid,
vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid, 2-hydroxy
ethyl methacrylate
phosphate.
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Preferred ionic polymeric de-coagulants (a) are selected from the group
consisting of a homo-
polymer of acrylic acid (or salts thereof) and a copolymer of a monomer
mixture consisting of
acrylic acid (or salts thereof) and acrylamide. Suitable ionic polymeric de-
coagulants (a) of this
category may include polymers in the Dispex or Sokalan product ranges
supplied by BASF.
5 Another particularly suitable category of ionic polymeric de-coagulants
(a) include anionic poly-
mers derived from ethylenically unsaturated monomers and said polymer
comprising repeating
monomeric units carrying pendant polyalkyleneoxy groups. Suitable ionic
polymeric de-
coagulants (a) may be prepared in accordance with US 6777517, US 2012/0035301
or CA
2521173.
10 Preferred ionic polymeric de-coagulants (a) include polymers comprising
repeating units derived
from monomers,
(i) an ethylenically unsaturated anionic or non-ionic monomer containing a
polymerisable
moiety (M) and having the structure
M ¨ R2¨ X ¨ (- CH2¨ CHR5¨ 0 -)i ( ¨ CH2¨ CH2¨ 0 ¨)m - ( - CH2 ¨ CHR3 ¨ 0 -),-,
¨ R4 (I)
15 in which
X is 0 or NH,
R2 is independently a single bond or a divalent linking group selected from
the group consisting
of ¨(CH2¨)p- and ¨0¨(CH2¨)s where p is a number from 1 to 6 and s is a number
from 1 to 6,
R3 and R5 are each independently a hydrogen or hydrocarbyl radical having 1-4
carbon atoms,
R4 is independently a hydrogen or a hydrocarbyl radical having 1-4 carbon
atoms or a moiety
having the structure ¨ ( ¨ CH 2¨ CH2¨ 0 ¨)k-Y
k is a number from 1 to 20
I is a number from 0 to 250;
m is a number from 1 to 300,
n is a number from 0 to 250;
Y is hydrogen or a hydrocarbyl radical having 1-4 carbon atoms,
and
(ii) at least one ethylenically unsaturated monomer carrying at least one
anionic functional
group different from component (i);
and
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(iii) optionally at least one ethylenically unsaturated non-ionic monomer,
different from
component (i).
In the present invention, M maybe any suitable polymerisable ethylenically
unsaturated moiety.
Preferably, M is selected from a vinyl moiety, an ethylenically unsaturated
carboxylic moiety, an
ethylenically unsaturated amide moiety, an allyl moiety or isoprenyl moiety.
More preferably, M is selected from the group consisting of:
H2C=C(R1)¨ (II);
H2C=C(R1)¨CH2¨ (Ill);
H2C=C(R1)¨00¨ (IV);
H000¨HC=C(R1)¨00¨ (V); and
¨0C¨HC=C(R1)¨00¨(V1),
in which R1 is hydrogen or methyl.
It will be apparent to the person skilled in the art in the field of
polyalkylene oxides that the num-
bers in regard to I, m and n mentioned are mean values of distributions.
It will be apparent to the person skilled in the art in the field of
polyalkylene oxides that the ori-
entation of the respective hydrocarbyl radicals R3 and R5 may depend on the
conditions in the
alkoxylation, for example on the catalyst selected for the alkoxylation in the
polymerisation reac-
tion of the copolymer of the present invention. The alkyleneoxy groups can
thus be incorporated
into the monomer (i) in the orientation ¨(¨CH2¨CH(R5)-0-)1¨ or else the
inverse orientation ¨(-
CH(R5)-0H2-0-)1¨ and the orientation ¨(¨CH2¨CH(R3)-0-),-,¨ or else the inverse
orientation ¨(¨
CH(R3)-CH2-0-)n¨. The representation in formula (I) shall therefore not be
regarded as being
restricted to a particular orientation of the R3 or R5 groups.
Monomer (i) of general formula (I) suitably contains the following preferred
features:
Preferably integers I and n are each zero.
Integer m is preferably from 5 to 250, more preferably from 10 to 200, even
more preferably
from 45 to 175 and most preferably from 45 to 175.
Preferably, R1 is hydrogen.
If R2 is not a single bond then preferably integer s is 4; or integer p is 1
or 2.
Preferably, M is a vinyl, or maleic mono ester group.
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One suitable group of monomers as monomer (i) of the general formula (I) is
vinyloxybutyl poly-
ethylene glycol, in which the polyethylene glycol moiety contains from 45 to
175 repeating eth-
ylenoxide units, preferably containing from 75 to 150 repeating ethylenoxide
units, more prefer-
ably containing from 100 to 150 repeating ethylenoxide units, particularly
from 110 to 140 re-
peating ethylenoxide units, more particularly from 120 to 140 repeating
ethylenoxide units. An
especially preferred monomer (i) of general formula (I)is the adduct of 129
moles of ethylene
oxide with 4-hydroxy butyl mono vinyl ether.
A further suitable group of monomers as monomer unit (i) of general formula
(I) is based on the
reaction of 4-hydroxy butyl vinyl ether which has been ethoxylated, then
butoxylated and then
ethoxylated. This group of monomers may be described as vinyloxybutyl
polyethylene glycol
polybutadiene glycol polyethylene glycol or may be defined as vinyloxybutyloxy
(E0)a (B0)b
(E0)c, in which EO represents repeating ethylenoxide units, BO represents
repeating butylene
units and each of a, b, c independently represents numbers. Suitably, a may be
from 5 to 75, b
may be from 1 to 30 and c may be from 0 to 20. Preferably, a may be from 10 to
50, b may be
.. from 2 to 20 and c may be from 0 to 20. More preferably, a may be from 15
to 40, b may be
from 5 to 20 and c may be from 0 to 10. More preferably still, a may be from
24 to 25, b may be
from 10 to 20 and c may be from 0 to 5. One particularly suitable monomer is
where a is from
24-25, b is from 15-17 and c is from 3-4.
Another suitable monomer (i) of the general formula (I) is poly (PO block-EO)
maleamide which
may be prepared by the reaction of Jeffamine Monoamines (M series) (available
from Hunts-
man) with maleic anhydride in the ratio of 1:1 to give the mono amide. By PO
block-EO it is un-
derstood that this means a block of propylene oxide units and a block of
ethylene oxide units.
The at least one ethylenically unsaturated monomers that carries an anionic
functional group of
category (ii) may be any suitable anionic ethylenically unsaturated monomer.
Suitable anionic
functional groups may include carboxylic acids, sulphonic acids, sulphuric
acids, phosphoric
acids or phosphonic acids. By referring to the specific ethylenically
unsaturated anionic mono-
mers we also include the corresponding salts thereof by this definition. We
also include the cor-
responding anhydride of an acid group in the definition of ethylenically
unsaturated anionic
monomers. Suitable monomers in this category include acrylic acid, methacrylic
acid, maleic
acid, fumaric acid, itaconic acid, ethacrylic acid, crotonic acid, mono esters
of ethylenically un-
saturated dicarboxylic acids, such as mono methyl maleate, mono methyl
fumarate, mono ethyl
maleate, mono n butyl maleate, and mono n butyl fumarate, styrene carboxylic
acids, maleic
anhydride, itaconic anhydride, 2-acrylamido-2-methylpropylene acid,
vinylsulfonic acid, allyl sul-
phonic acid, vinyl phosphonic acid, 2-hydroxy ethyl methacrylate phosphate.
A still further type of suitable monomers (i) of general formula (I) are based
on methacrylic es-
ters and acrylic esters. Examples of these are mono methacrylate adduct of
ethylene oxide
units. Typical examples of these may be found in US 5707445, particularly in
the examples in
column 7 by reference to monomers A-1 (mono methacrylate of adduct of methanol
with eth-
ylene oxide (EO) units (average number of EO units of 115)); A-2 (mono
methacrylate adduct of
methanol with EO repeating units (average number 220)); A-3 (mono methacrylate
adduct of
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methanol with repeating EO units (average number 280)); A-5 (block adduct of
acrylic acid with
propylene oxide (PO) units and EO units (average number 135)); A-6 (block
adduct of acrylic
acid with E0 and PO (average number of E0 molecules 135 and average number of
PO mole-
cules added 5)); and A-8 (mono methacrylate of adduct of methanol with EO
(average number
5 of EO molecules 100)).Preferably monomer component of category (ii) is
either acrylic acid (or
salts thereof), maleic anhydride or maleic acid (or salts thereof).
Suitable ethylenically unsaturated non-ionic monomers of category (iii) may be
any suitable
non-ionic ethylenically unsaturated monomer that is different from the
monomers of category (i)
and be copolymerisable with the monomers of categories (i) and (ii).
Desirably, these mono-
10 .. mers may be selected from the group consisting of acrylamide,
methacrylamide, hydroxy alkyl
acrylate, hydroxy alkyl methyl acrylate, vinyl acetate, vinyl alcohol, allyl
alkyl ether, styrene, and
alkyl acrylates.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of
hydroxyethyl
acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable
hydroxyalkyl methacry-
lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and
hydroxybutyl methac-
rylate.
Suitable 01-8 alkyl acrylates as non-ionic comonomers may include methyl
acrylate, ethyl acry-
late, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl
acrylate, isobutyl acrylate,
tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or cyclohexyl
acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl
ether, allyl ethyl
ether, allyl n-propyl ether or allyl isopropyl ether.
The ranges of the respective repeating units are suitably as follows:
Monomer (i) is preferably from 1 to 50 moles %; monomer (ii) is preferably
from 50 to 99 mole
%; and monomer (iii) is preferably from 0 to 33 mole %. More preferably,
monomer (i) is from 5
to 40 mole %; monomer (ii) from 60 to 95 mole %; and monomer (iii) from 0 to
25 mole %. Even
more preferably, monomer (i) is from 10 to 30 mole %; monomer (ii) from 70 to
90 mole %; and
monomer (iii) is preferably 0%.
The weight average molar mass of the ionic polymeric de-coagulant (a) formed
from monomers
(i), (ii) and optionally (iii) is preferably from 1000 to 100,000 g/mole, more
preferably from 5000
to 70,000 g/mole, even more preferably from 10,000 to 65,000 g/mole, more
preferably still from
20,000 to 60,000 g/mole, especially from 25,000 to 60,000 g/mole and most
preferably from
30,000 to 60,000 g/mole.
The weight average molar mass may be determined by gel permeation
chromatography (GPO)
with the following method: column combination: Shodex OH-Pak SB 804 HQ and OH-
Pak SB
802.5 HQ from Showa Denko, Japan; eluent: 80 vol % aqueous solution of HCO2NH4
(0.05
mo1/1) and 20 vol% Me0H; injection volume 100 pl; flow rate 0.5 ml/min. The
weight average
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molar mass may be calibrated using standards from PSS Polymer Standard
Service, Germany.
For the UV detector, poly(styrene-sulfonate) standards may be used, and
poly(ethylene oxide)
standards for the RI detector. The weight average molar mass may then be
determined using
the results of the RI detector.
The preparation of suitable polymeric products containing monomers (i) and
(ii) and optionally
containing component (iii) is described in US 6777517, US 2012/0035301 or CA
2521173.
One particularly suitable group of ionic polymeric de-coagulant (a) is formed
from the terpolymer
of vinyloxybutyl polyethylene glycol (i); acrylic acid as a monomer (ii); and
maleic anhydride as a
further monomer (ii). The polyethylene glycol moiety preferably contains from
45 to 175 repeat-
ing ethylenoxide units, preferably containing from 75 to 150 repeating
ethylenoxide units, more
preferably containing from 100 to 150 repeating ethylenoxide units,
particularly from 110 to 140
repeating ethylenoxide units, more particularly from 120 to 140 repeating
ethylenoxide units.
Particularly preferably the monomer (i) is the adduct of 129 moles of ethylene
oxide with 4-
hydroxybutyl monovinyl ether. The molar ratio of the aforesaid three monomers
is preferably
0.8-1.2/4/0.4-0.8 and suitably has a weight average molar mass of from 45,000
to 60,000
g/mole. The preparation of a particularly suitable polymer for use as the
ionic polymeric de-
coagulant (a) is described in US 2012/0035301 on page 4 under heading Polymer
1.
Another suitable group of ionic polymeric de-coagulant (a) is formed from the
terpolymer of vi-
nyloxy butyl polyethylene glycol polybutylene glycol polyethylene glycol (as
described above) (i):
acrylic acid as a monomer (ii); and maleic anhydride as a further monomer
(ii). The monomer (i)
vinyloxybutyloxy (E0)a (B0)b (E0)c, in which EO and BO have each been defined
above and
in which suitably a may be from 5 to 75, b may be from 1 to 30 and c may be
from 0 to 20. Pref-
erably, a may be from 10 to 50, b may be from 2 to 20 and c may be from 0 to
20. More prefer-
ably, a may be from 15 to 40, b may be from 5 to 20 and c may be from 0 to 10.
More preferably
still, a may be from 24 to 25, b may be from 10 to 20 and c may be from 0 to
5. One particularly
suitable monomer is where a is from 24-25, b is from 15-17 and c is from 3-4.
The molar ratio of
the aforesaid three monomers is suitably 2-5/4/0.8-1.2 and the weight average
molar mass of
from 15,000 to 45,000 g/mole.
Other suitable polymers as ionic polymeric de-coagulants (a) are described in
US
2012/0035301, particularly the examples.
Further suitable polymers as ionic polymeric de-coagulants (a) include
copolymers of methacryl-
ic or acrylic esters of formula (I) with ethylenically unsaturated carboxylic
acids or corresponding
salts such as acrylic acid (or salts thereof), methacrylic acid (or salts
thereof) or maleic acid (or
salts thereof or the anhydride). Suitable methacrylic esters of formula (I)
would include mono-
mers A-1, A-2, A-3, A-5, A-6 and A-8 given in US 5707445 (described above).
Suitable exam-
ples of such suitable polymers for this application are given in US 5707445
for instance the
Preparative Example 3 and Preparative Example 5. Examples of other suitable
polymers are
also given in EP 1142847 A2 and particularly in Reference Example 3 and
Reference Example
4.
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Yet further suitable polymers as ionic polymeric de-coagulants (a) include
copolymers of poly-
ethylene glycol mono methyl ether methacrylate copolymers with ethylene glycol
methacrylate
phosphate optionally with methacrylic acid. Desirable examples of these
polymers are given in
US 2008/146700 and with specific reference to Table 1 and in particular
Polymer Numbers 5-8,
5 14 and 15.
By water-soluble in respect of the ionic polymeric de-coagulant (a), we mean
that the polymers
exhibit a solubility in water of at least 5 g per 100 ml of water at 25 C.
The ionic polymeric de-coagulant (a) may suitably have a charge density of
from 0.2 to 10
meq/g (milliequivalents per gram), preferably from 0.3 to 8 meq/g, more
preferably from 0.5 to 5
10 meq/g and most preferably from 0.8 to 3 meq/g.
The at least one ionic polymeric de-coagulant (a) may be used in conjunction
with other addi-
tives. This may be by the inclusion of one or more additives together with the
at least one ionic
polymeric de-coagulant (a), for instance as at least one compound present as a
mixture togeth-
er with the at least one ionic polymeric de-coagulant (a). Examples of typical
additives that may
15 be used in conjunction with the at least one ionic polymeric de-
coagulant (a) include polyeth-
ylene glycol (PEG), polyethylene glycol derivatives (such as monofunctional
polyethylene glycol
monoalkyl ethers) or polyvinyl alcohol. Suitable polyethylene glycols may have
weight average
molar masses of up to 50,000 g/mol but are usually within the range of from 50
g/mol to 30,000
g/mol, typically in the range of from 100 to 20,000 g/mol, for instance from
200 to 20,000 g/mol
20 or 200 to 10,000 g/mol, such as from 200 to 5000 g/mol, typically from
200 to 1000 g/mol or
from 300 to 500 g/mol. The polyethylene glycols may have any particular
geometry, for instance
linear, branched, star, comb structures. Suitable polyethylene glycols are
commercially availa-
ble and may be available, for instance from Dow Chemical under the tradename
Carbowax 0,
or from BASF under the tradename Pluriol 0 E or from Clariant under the name
Polyglykol 0 M.
The at least one ionic polymeric de-coagulant (a) may be a mixture of
different ionic polymeric
de-coagulants. Such a mixture may include a first mixture component based on
one or more of
any of the aforementioned ionic, especially anionic, polymers derived from
ethylenically unsatu-
rated monomers and being a polymer comprising repeating monomeric units
carrying pendant
polyalkyleneoxy groups and a second mixture component being one or more
different ionic pol-
ymeric de-coagulants as described herein. Such different ionic polymeric de-
coagulant as sec-
ond mixture component may be a homopolymer or copolymer of acrylic acid (or
salts thereof),
for instance any of those polymer types analogous to the Dispex or Sokalan
product ranges.
Preferably the mixture of different ionic polymeric de-coagulants comprises as
first mixture
component being a polymer in the aforementioned category formed from monomers
(i), (ii), and
optionally (iii) and the second mixture component being an anionic copolymer
or anionic homo-
polymer, particularly of the polymer types analogous to Dispex or Sokalan
product ranges.
The polymeric flocculent (b) should be a polymer having an intrinsic viscosity
of at least 5 dl/g
(measured at 25 C in 1 M NaCI). The polymer may be non-ionic, anionic,
amphoteric or cation-
ic. Typically, this may be formed from ethylenically unsaturated monomers. In
the case of a non-
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ionic polymeric flocculent the polymer may be derived from at least one non-
ionic ethylenically
unsaturated monomer. In the case of an anionic polymeric flocculent, the
polymer may be de-
rived from at least one anionic ethylenically unsaturated monomer, optionally
including at least
one ethylenically unsaturated non-ionic monomer. When the polymeric flocculent
is cationic, it
may be derived from one or more ethylenically unsaturated cationic monomers,
optionally in
combination with an ethylenically unsaturated non-ionic monomer. Where the
polymeric floccu-
lent is amphoteric, this may be derived from ethylenically unsaturated anionic
monomers and
ethylenically unsaturated cationic monomers, optionally in combination with
ethylenically un-
saturated non-ionic monomers. Preferably, the polymeric flocculent (b) is a
polymer formed
from repeating units derived from at least one ethylenically unsaturated
monomer bearing an
anionic group and optionally at least one ethylenically unsaturated non-ionic
monomer.
Preferably still, the polymeric flocculent (b) is a water-soluble polymer
derived from ethylenically
unsaturated monomers selected from the group consisting of homopolymers of one
or more
ethylenically unsaturated acid monomers (or salts thereof); and copolymers
formed from a
monomer mixture comprising of (A) one or more ethylenically unsaturated acid
monomers (or
salts thereof), (B) one or more ethylenically unsaturated non-ionic monomers
selected from the
group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, vinyl
acetate, vinyl al-
cohol, allyl alkyl ether, styrene and 01-8 alkyl acrylates (C) one or more
other ethylenically un-
saturated monomers different from (A) and (B). Ethylenically unsaturated
monomers in category
(C) may include other ethylenically unsaturated non-ionic monomers not
specified in category
(B) or alternatively it may be ethylenically unsaturated monomers bearing a
cationic functional
group.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of
hydroxyethyl
acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable
hydroxyalkyl methacry-
lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and
hydroxybutyl methac-
rylate. Suitable 01_8 alkyl acrylates as non-ionic comonomers may include
methyl acrylate, ethyl
acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl
acrylate, isobutyl acry-
late, tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or
cyclohexyl acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl
ether, ally! ethyl
ether, allyl n-propyl ether or allyl isopropyl ether.
The at least one ethylenically unsaturated acid monomers of category (A) may
be any suitable
anionic ethylenically unsaturated monomer. Suitable acid groups may include
carboxylic acids,
sulphonic acids, sulphuric acids, phosphoric acids or phosphonic acids. By
referring to the spe-
cific ethylenically unsaturated acid monomers we also include the
corresponding salts thereof
by this definition. We also include the corresponding anhydride of an acid
group in the definition
of ethylenically unsaturated acid monomers. Suitable monomers in this category
include acrylic
acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, ethacrylic
acid, crotonic acid,
mono esters of ethylenically unsaturated dicarboxylic acids, such as mono
methyl maleate,
mono methyl fumarate, mono ethyl maleate, mono n-butyl maleate, and mono n-
butyl fumarate,
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styrene carboxylic acids, maleic anhydride, itaconic anhydride, 2-acrylamido-2-
methylpropylene
acid, vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid, 2-
hydroxy ethyl methacrylate
phosphate.
When the polymeric flocculant (b) is a polymer comprising components (A), (B)
and contains
component (C), desirably the other ethylenically unsaturated monomers (C) may
be selected
from one or more cationic monomers, provided that the overall anionic
equivalent content is
greater than the overall cationic equivalent content. Suitably, the one or
more cationic mono-
mers are included in the monomer mixture in an amount of up to 10 mol % total
cationic mono-
mer based on the total molar content of monomers in the monomer mixture.
More preferably, the polymeric flocculant (b) is a copolymer of acrylamide
with (meth)acrylic
acid (or salt thereof) or a homopolymer of (meth)acrylic acid (or salt
thereof).
The polymeric flocculant (b) may desirably be any anionic homopolymer or
anionic copolymer
that contains multivalent or monovalent counterion. Typically, the multivalent
or monovalent
counterion containing homopolymer or copolymer would be the multivalent or
monovalent salt of
the copolymer. Suitably, the multivalent counterion may be formed from
alkaline earth metals,
group IIla metals, transition metal etc. Preferable multivalent counterions
include magnesium
ions, calcium ions, aluminium ions etc. Desirably, the monovalent counterion
may be formed
from alkali metals or ammonium. Preferable monovalent counterions include
lithium ions, sodi-
um ions, potassium ions, ammonium ions etc. Suitable homopolymers or
copolymers containing
multivalent counterions may include repeating units of magnesium diacrylate,
calcium diacrylate
and aluminium triacrylate. Suitable copolymers containing monovalent
counterions include lithi-
um acrylate, sodium acrylate, potassium acrylate and ammonium acrylate.
Desirably, the copolymer comprises repeating units of (meth)acrylamide and an
ethylenically
unsaturated anionic monomer contains a sodium counterion, a potassium
counterion, an am-
monium counterion, a calcium counterion or a magnesium counterion. Preferably,
the copoly-
mer contains a calcium counterion. More preferably, the copolymer is of
acrylamide and an eth-
ylenically unsaturated anionic monomer containing a calcium counterion.
Typically, the multivalent or monovalent counterion is contained in the
homopolymer or copoly-
mer of the polymeric flocculant (b) in a significant amount relative to the
number of repeating
units of the ethylenically unsaturated anionic monomer. Normally, the molar
equivalent of multi-
valent or monovalent counterion to repeating anionic monomer units is at least
0.10:1. Suitably,
the molar ratio equivalent may be from 0.15:1 to 1.6:1, normally from 0.20:1
to 1.2:1, preferably
from 0.25:1 to 1:1.
The multivalent or monovalent counterion containing copolymer may be
obtainable by copoly-
.. merisation of ethylenically unsaturated anionic monomer which is already in
association with the
multivalent or monovalent counterion, for instance multivalent or monovalent
cation salts of eth-
ylenically unsaturated anionic monomer with (meth)acrylamide.
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Thus, the multivalent or monovalent counterion containing copolymer, may be
derived from a
monomer mixture comprising a multivalent or monovalent cation salt of an
ethylenically unsatu-
rated anionic monomer and (meth)acrylamide. The ethylenically unsaturated
anionic monomer
salt may be present in an amount in the range of from 5% to 95% by weight,
based on the total
weight of the monomers. Desirably, the amounts of the respective monomers used
to form the
copolymer may be, for instance,
from 5% to 95% by weight of multivalent or monovalent cation salt of an
ethylenically un-
saturated anionic monomer; and
from 5% to 95% by weight of (meth) acrylamide.
Preferably, the amount of multivalent or monovalent cation salt of the
ethylenically unsaturated
anionic monomer may be from 5% to 85% by weight, such as from 5% to 70% by
weight, typi-
cally from 10% to 60% by weight, often from 15% to 50% by weight, desirably
from 20% to 45%
by weight, for instance from 25% to 40% by weight; and the amount of
(meth)acrylamide may
be from 50% to 95% by weight, such as 30% to 95% by weight, typically from 40%
to 90% by
weight, often from 50% to 85% by weight, desirably from 55% to 80% by weight,
for instance
from 60% to 75% by weight.
Preferably, polymerisation is effected by reacting the aforementioned monomer
mixture using
redox initiators and/or thermal initiators. Typically, redox initiators
include a reducing agent such
as sodium sulphite, sodium metabisulphite, sulphur dioxide and an oxidising
compound such as
ammonium persulphate or a suitable peroxy compound, such as tertiary butyl
hydroperoxide
etc. Redox initiation may employ up to 10,000 ppm (based on weight of aqueous
monomer) of
each component of the redox couple. Preferably though, each component of the
redox couple is
often less than 1000 ppm, typically in the range from 1 to 100 ppm, normally
in the range from 4
to 50 ppm. The ratio of reducing agent to oxidising agent may be from 10:1 to
1:10, preferably in
the range from 5:1 to 1:5, more preferably from 2:1 to 1:2 for instance around
1:1.
The polymerisation of the monomer mixture may be conducted by employing a
thermal initiator
alone or in combination with other initiator systems, for instance redox
initiators. Thermal initia-
tors would include suitable initiator compound that releases radicals at an
elevated temperature,
for instance azo compounds, such as azobisisobutyronintrile (Al BN), 4,4'-azo
bis-(4-
cyanovalereic acid) (ACVA). Typically, thermal initiators are used in an
amount of up to 10,000
ppm, based on weight of aqueous monomer. In most cases, however, thermal
initiators are
used in the range from 100 to 5000 ppm, preferably from 200 to 2000 ppm, more
preferably
from 300 to 700 ppm, usually around from 400 to 600 ppm, based on the weight
of the aqueous
monomer mixture.
Typical methods of preparation of the multivalent or monovalent counterion
containing copoly-
mer are given in WO 2017084986.
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Intrinsic viscosity of the polymeric flocculent (b) may be determined by first
preparing a stock
solution. This may be achieved by placing 1.0 g of copolymer in a bottle and
adding 199 ml of
deionised water. This mixture may then be mixed for 4 hours, for instance on a
tumble wheel, at
ambient temperature (25 C). Diluted solutions may then be prepared by, for
instance, taking
.. 0.0g, 4.0 g, 8.0 g, 12.0 g and 16.0 g, respectively, of the aforementioned
stock solution and
placing each into 100 ml volumetric flasks. In each case, 50 ml of sodium
chloride solution (2 M)
should then be added by pipette and the flask then filled to the 100 ml mark
with deionised wa-
ter and in each case the mixtures shaken for five minutes until homogenous. In
each case, the
respective diluted copolymer solutions are in turn transferred to an Ubbelohde
viscometer and
.. the measurement carried out at 25 C with the capillary viscometer Lauda
iVisc. As such, the
reduced specific viscosity of each of the dilute solution may be calculated
and then extrapolated
to determine the intrinsic viscosity of the polymer, as described in the
literature.
Suitably, polymeric flocculent (b) may have an intrinsic viscosity in the
range of from 5 to 30
dl/g, desirably from 5 to 25 dl/g, such as from 6 to 20 dl/g, for instance
from 7 to 20 dl/g, often
.. from 9 to 19 dl/g, typically from 10 to 18 dl/g, normally from 12 to 18
dl/g.
In one preferred form, the polymeric flocculent (b) is water-soluble. By water-
soluble we mean
that the polymer has a gel content measurement of less than 50% gel. The gel
content meas-
urement is described below.
The gel content may be determined by filtering a stock solution (preparation
of a stock solution
is described above in the method of measuring intrinsic viscosity) through a
sieve with a 190
pm mesh size. The residue which stays in the filter is washed, recovered,
dried (110 C) and
weighed, and the percentage of undissolved polymer is calculated (weight of
dry residue from
the filter [g] /weight of dry polymer before filtration [g]). Where necessary,
this provides a quan-
tifiable confirmation of the visual solubility evaluation.
.. The optional cationic coagulant (c) is suitably a polymeric material having
a weight average mo-
lar mass of from 10,000 to 2 million g/mol. Suitable polymers include polymers
of diallyl dialkyl
ammonium halide, for instance the homopolymers of diallyl dimethyl ammonium
chloride
(DADMAC). Suitable polymers may be formed from other cationic monomers such as
quater-
nary ammonium salts of acrylate esters, for instance quaternary ammonium salts
of dialkyl
.. amino alkyl (meth) acrylate, such as the methyl chloride quaternary
ammonium salt of dimethyl
amino ethyl acrylate (DMAEA-q) or the methyl chloride quaternary ammonium salt
of dimethyl
amino ethyl methacrylate (DMAEMA-q). Further suitable polymers may be formed
from cationic
monomers based on the quaternary ammonium salts of amino alkyl acrylamides,
including the
quaternary ammonium salts of dialkyl amino alkyl (meth) acrylamides, for
instance acrylamido
propyl trimethylammonium chloride (APTAC) or methacrylamido propyl
trimethylammonium
chloride (MAPTAC). The aforesaid cationic monomers may be as homopolymers or
as copoly-
mers, for instance copolymers with acrylamide, such as DADMAC acrylamide
copolymers, AP-
TAC acrylamide copolymers, MAPTAC acrylamide copolymers, DMAEA-q acrylamide
copoly-
mers, and DMAEMA-q acrylamide copolymers.
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Other suitable polymers include polyamines, for instance partially or fully
hydrolysed polyvinyl
formamides containing repeating vinyl amine units. Other polymers include
polyethyleneimines,
polymers of alkyl amines with formaldehyde and/or epichlorohydrin, and
polycyandiamides.
Typical doses of the polymeric de-coagulant(a) may range from 0.1 to 1000 g
polymer per
5 tonne of solids content of the aqueous slurry, suitably from 1 to 800 g
per tonne, such as 10 to
600 g per tonne, for instance 20 to 500 g per tonne, desirably from 50 to 400
g per tonne, for
instance from 75 to 350 g per tonne, suitably from 100 to 300 g per tonne, for
instance from 150
to 250 g per tonne.
Typical doses of the polymeric flocculant (b) may range from 20 to 2000 g of
polymer per tonne
10 of solids content of the aqueous slurry. Desirably, this may be from 40
or 50 to 1500 g per
tonne, suitably from 75 to 1000 g per tonne, often from 90 to 750 g per tonne,
usually from 100
to 500 g per tonne.
The exact doses of each of the two components may depend on the particular
aqueous slurry,
including the particular particulate mineral material of the slurry and the
solids content of the
15 slurry. The optional cationic coagulant (c) may be applied to the
aqueous suspension in doses
in the ranges from 10 to 1000 g/tonne based on active weight of coagulant on
dry weight of
aqueous slurry, for instance in the range of from 25 to 750 g/tonne, or from
50 to 500 g/tonne,
or from 100 to 250 g/tonne.
Suitably, the particulate solids of the aqueous slurry comprise mineral
solids. Typically, the par-
20 ticulate solids may for instance contain filter cake solids or tailings.
Often, the aqueous slurry
may be an underflow from a gravimetric thickener, a thickened plant waste
stream or alterna-
tively may be an unthickened plant waste stream. For instance, the aqueous
slurry may com-
prise phosphate slimes, gold slimes or wastes from diamond processing. Typical
aqueous slur-
ries include slurries of mineral sands tailings, zinc ore tailings, lead ore
tailings, copper ore tail-
25 ings, silver ore tailings, uranium ore tailings, nickel ore tailings,
iron ore tailings, coal fines tail-
ings, oil sands tailings or red mud. The aqueous slurry suitable for treatment
in accordance with
the present invention may include the concentrated suspension from the final
thickener or wash
stage of a mineral processing operation. Thus, the aqueous slurry may
desirably result from a
mineral processing operation. Preferably, the suspension comprises tailings.
Suitably, the par-
ticulate solids contained in the aqueous slurry may comprise at least some
solids which are hy-
drophilic, for instance water swelling clays. More preferably, the particulate
solids of the aque-
ous slurry may be derived from tailings from a mineral sands process, coal
fines tailings, oil
sands tailings, phosphate tailings or red mud.
The concentration of the aqueous slurry will tend to vary according to the
particular type of sub-
strate. In general, the aqueous slurry can often be a slurry of thickened
tailings, for instance a
thickened tailings suspension flowing as an underflow from a thickener, for
instance a gravimet-
ric thickener, or other stirred sedimentation vessel. Suitably, the aqueous
slurry may have a
solids content in the range of from 25 to 70 % by total weight of aqueous
slurry, preferably from
30 to 70% by weight, for instance from 45% to 65% by weight. Preferably, the
solids content of
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the aqueous slurry will often be from 30 to 50%, frequently from 30 to 45% by
total weight of
the aqueous slurry. When a pre-thickening stage occurs, the sand fraction
(<44pm) solids may
already be combined with the fine solids fraction, or may be combined with the
tailings stream
subsequently, after the thickening stage.
Suitably, the aqueous slurry containing the particulate material may be an
underflow stream
which flows from a sedimentation vessel in which a first suspension of the
particulate mineral
material is separated into a supernatant layer comprising an aqueous liquor
and a thickened
layer which is removed from the vessel as an underflow. It would be this
underflow which would
be subjected to the treatment according to the present invention. It would not
be possible to
achieve the objectives of the invention by adapting the separation in a
conventional sedimenta-
tion vessel as the yield stress of the thickened layer would be so high that
it would be impossi-
ble to stir the thickened layer or remove the thickened layer from the
conventional sedimenta-
tion vessel as an underflow. Furthermore, such solids would not be able to
flow as an underflow
from the vessel.
Aqueous slurries may not necessarily have a sand to fines ratio within the
range of 0.5:1 to 5:1.
For instance, whole tailings (WT) have sand to fines ratios of greater than
4:1 and mostly tend
to be greater than 5:1 and may be as high as 20:1. Composite tailings (CT)
also have high
sand to fines ratios typically more than 3:1 and in some cases more than 5:1
and may be as
high as 6:1 or 7:1. On the other hand fluid fines tailings (FFT), thin fines
tailings (TFT), thick-
ened fines tailings (ThFT) and mature fines tailings (MFT) all tend to have
very low sand to
fines ratios. FFT tend to have sand to fine ratios significantly below 1:1 and
MFT tend to have
much lower sand contents typically less than 0.3:1, for instance less than
0.25:1.
The sand to fines ratios of aqueous slurries not having a sand to fines ratio
within the range of
0.5:1 to 5:1, or 1:1 to 4:1 or 1:1 to 3:1 may be adjusted to a sand to fines
ratio within the scope
of the present invention, including any of the preferred sand to fines ratios
recited herein.
For aqueous slurries where the sand to fines ratios fall below 0.5:1, for
instance, as in the case
of MFT slurries, and desirably even where the sand to fines ratios fall below
1:1, for instance,
as in the case of FFT slurries, TFT slurries and ThFT slurries, the sand to
fines ratio may be
increased. One way of achieving this is to combine sand with the aforesaid
MFT, FFT, TFT or
ThFT slurries. The sand may be a concentrated sand fraction, for instance the
underflow from a
cyclone processing whole tailings (WT). Another way of carrying this out would
be to mix the
aforesaid MFT, FFT, TFT or ThFT slurries with whole tailings (WT). In both
cases the propor-
tions of sand fraction or whole tailings to the MFT, FFT, TFT or ThFT slurries
should be such
that the so formed composite tailings (CT) should have a sand to fines ratio
of from 0.5:1 to
5:1, preferably from 1:1 to 4:1, more preferably from 1:1 to 3:1 and more
preferably still be-
tween 1:1 and 2:1.
Where the aqueous slurries have a sand to fines ratio greater than 5:1,
preferably greater than
4:1 and more preferably greater than 3:1, as in the case of whole tailings
(WT) or even some
conventional composite tailings (CT), the adjustment of the sand to fines
ratio should be a re-
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duction of the sand content. One way of conducting this would be to pass whole
tailings (WT)
through a screen which filters out large coarse size sand particles such as
greater than 120 pm
or preferably greater than 100 pm. This may also be achieved by passing the
aqueous slurry,
for instance whole tailings, through a cyclone which cuts at the desired
particle size, for in-
stance 120 pm or 100 pm, to remove the larger particle size sand. This removal
of some of the
sand would serve to reduce the sand to fines ratio to the desired level.
There are a number of ways in which the treatment system can be applied to the
aqueous slurry
including addition to any of the components forming the aqueous slurry such as
precursor slur-
ries or other components such as sand.
In accordance with one aspect of the inventive process the aqueous slurry may
be formed from
a first precursor aqueous slurry in which the sand to fines ratio is below
0.5:1, suitably below
1:1, and the sand to fines ratio may be adjusted to increase the sand to fines
ratio by either,
(a) combining the first precursor aqueous slurry with sand; and/or
(b) combining the first precursor aqueous slurry with a second precursor
aqueous slurry,
which second precursor aqueous slurry has a sand to fines ratio of greater
than 3:1, suitably
greater than 4:1 and especially suitably greater than 5:1,
and thereby forming the aqueous slurry,
in which the treatment system or components thereof desirably would be applied
to any one or
more of the first precursor aqueous slurry, the sand component, the second
precursor aqueous
slurry and/or the aqueous slurry.
In one suitable embodiment of this aspect of the invention the sand in (a) may
be in the form of
a sand stream, preferably the underflow sand stream from a cyclone processing
whole tailings
(WT). Desirably, the first precursor aqueous slurry is selected from the group
consisting of ma-
ture fines tailings (MFT), fluid fines tailings (FFT), thin fines tailings
(TFT), thickened fines tail-
ings (ThFT). The second precursor aqueous slurry may desirably be whole
tailings (WT).
In accordance with a further aspect of the inventive process the aqueous
slurry may be formed
from a second precursor aqueous slurry in which the sand to fines ratio is
greater than 3:1, suit-
ably greater than 4:1 and especially suitably greater than 5:1, and the sand
to fines ratio desira-
bly would be adjusted to decrease the sand to fines ratio by separating sand
particles having a
particle size greater than a predetermined size limit, preferably greater than
100 pm, from the
second precursor aqueous slurry thereby,
and thereby forming the aqueous slurry,
in which the treatment system or components thereof are applied to any one or
more of the
second precursor aqueous slurry and/or the aqueous slurry. The predetermined
size limit may
be set at any level sufficient to remove sufficient sand particles in order to
provide an aqueous
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slurry of the desired sand to fines ratio in accordance with the invention.
This may, for instance,
be greater than 100 pm or in some cases greater than 110 pm or in other cases
greater than
120 pm, depending upon the particle size distribution and sand content of the
second precursor
aqueous slurry. The second precursor aqueous slurry may, for instance, be
whole tailings (WT).
-- Preferably, the separation of the sand from the second precursor aqueous
slurry is conducted
using a cyclone having a screen having a mesh size sufficient to remove the
sand particles hav-
ing a particle size greater than the predetermined size limit.
Preferably, the aqueous slurry of particulate material comprises flowing as
slurry of mature fines
tailings (MFT) and/or fluid fines tailings (FFT) and/or thickened fines
tailings (ThFT) along a
-- conduit and in which a slurry of sand is combined with the slurry of mature
fines tailings and/or
fluid fines tailings and/or thickened fines tailings (ThFT) to provide a
combined tailings stream
(CbT) having the desired sand to fines ratio of from 0.5:1 to 5:1, wherein the
components of the
treatment system are applied to (i) the mature fines tailings and/or fluid
fines tailings and/or
thickened fines tailings (ThFT); and/or (ii) the combined tailings (CbT)
stream, and in which the
-- so treated combined tailings (CbT) stream is fed to a deposition area.
Preferably the ionic poly-
meric de-coagulant (a) is either fed into the slurry of MFT and/or FFT and/or
ThFT; fed into the
sand slurry; or fed into the combined tailings stream (CbT) and thereafter the
polymeric floccu-
lant (b) is added to the so treated combined tailings stream (CbT).
Optionally, the cationic coag-
ulant (c) may be added to the combined tailings stream (CbT) either before, or
preferably after
-- the addition of the flocculant (b).
It may be desirable in some cases to add the polymeric flocculant (b) to the
aqueous slurry as it
exits the conduit for instance pipeline. In other cases, it may be desirable
to add the flocculant
prior to the aqueous slurry exiting the outlet of the conduit, or more
specifically pipeline, for in-
stance less than 100 m, less than 50 m and desirably less than 10 m from the
outlet. In gen-
-- eral, the polymeric flocculant (b) desirably would be added to the aqueous
slurry in the conduit
or pipeline and close to the outlet, for instance less than 50 m from the
outlet, for instance from
0.1 to 30 m from the outlet, or from 0.5 to 20 m from the outlet, or from 1 to
10 m from the out-
let, or even from 1 to 5 m from the outlet.
Typically, the aqueous slurry is transferred by pumping along a conduit to a
deposition area.
-- The conduit can be any convenient means for transferring the aqueous slurry
to the deposition
area and may, for instance, be a pipeline or even a trench. The deposition
area may be a tail-
ings dam or lagoon or may be adjacent to a tailings dam or lagoon, or
preferably an open min-
ing void or pit.
Normally the aqueous slurry would be transferred continuously to the
deposition area i.e. with-
-- out interruption of the flow. However, in some cases it may be desirable to
transfer the aqueous
slurry first to a holding vessel or pond, before being transferred to the
deposition area.
Suitably, the aqueous slurry is transferred to the deposition area through a
conduit, for instance
a pipeline. Normally, such a conduit, for instance pipeline, would have an
outlet from which the
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aqueous slurry exits as it flows to the deposition area. Typically, the outlet
of the conduit, for
instance pipeline, is at the deposition area or may be close to the deposition
area, for instance
less than 20 m, usually less than 10 m and desirably less than 5 m from the
deposition area. In
such cases where the conduit or more specifically pipeline is close to the
deposition area, the
aqueous slurry should be able to flow into the deposition area.
Desirably the so treated combined tailings stream (CbT) is fed into a void or
impoundment at
the deposition area, in which the void or impoundment has a depth of at least
5 m and the de-
posited solids are allowed to separate from the released supernatant liquid
and consolidate.
Desirably, the separated solids form a relatively homogeneous deposit with
minimal segregation
of the fines and sand particles. The void or impoundment area may have a depth
of at least 10
m, for instance at least 15 m or suitably at least 20 m. The depth may be as
much as 50 m or
even as much as 75 m or as much as 100 m or more. Thus, the void or
impoundment may have
a depth in the range of from 5 m to 100 m, from 10 m to 75 m, from 15 m to 50
m or from 20 m
to 40 m. This method of deep void disposal is sometimes referred to as Deep
Pour. Deep Pour
technique is believed by the inventors to be analogous to the technique
described in Section 4
of the COSIA document entitled, "Deep Fines-Dominated (Cohesive) Deposits" and
available on
the 005 IA website
(https://www.cosia.ca/uploads/documents/id7/TechGuideFluidTailingsMgmt_Aug2012.
pdf).
The supernatant liquid separated from the so treated slurry should form above
the particulate
solids deposited in the void or impoundment. Generally, the supernatant liquid
may desirably be
continually or periodically removed from the void or impoundment area.
Alternatively, the so treated combined tailings stream may be fed onto a beach
surface at the
deposition area and form thin layers of newly deposited beach material which
dewaters through
drainage and evaporation. The beached surface may have an angle of incline of
from 0.50 and
10 .
In some instances, in accordance with the invention, the deposition of the
solids is controlled to
build up relatively narrow bands of tailings which can also dewater quickly
through evaporation,
prior to adding a new layer of treated waste material on top. This technique
of using narrow
band disposal may sometimes be referred to as "Thin Lift". In general, the
deposition of the so
treated aqueous slurry may be onto a beached surface, for instance as
described in the previ-
ous paragraph. The inventors believe that the "Thin Lift" method of disposal
in regard to the oil
sands industry is analogous to the technique described in section 3 of the
aforementioned CO-
SIA document, entitled, "Thin Layered Fines Dominated Deposits". This document
uses from
0.1 to 0.5 m as a typical thickness for each lift.
Outside the oil sands industry, for instance in the alumina industry, the
invention may also be
employed by the deposition of thin layers, having a thickness of up to 0.5 m.
For instance, the
so treated material at a deposition area, such as onto a beached surface, as
described above,
the analogous technique may be referred to as "Dry Stacking". A general
description for this
type of technique in the alumina industry is described, particularly in
section 3, in the paper giv-
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en by DJ Cooling (Alcoa World Alumina Australia) to the Paste 2007 Conference
in Perth, Aus-
tralia. The paper is entitled, "Improving the Sustainability of Residue
Management Practices ¨
Alcoa World Alumina Australia", Australian Centre for Geo-mechanics, Perth,
ISBN 0-9756756-
7-2.
5 In one aspect of the invention the treatment system may comprise adding
the ionic polymeric
de-coagulant (a) to the aqueous slurry of particulate material before adding
the polymeric floc-
culent (b). Typically, aqueous slurry of particulate material may first be
treated by the addition of
the ionic polymeric de-coagulant (a) and then the so treated slurry subjected
to a mixing stage
followed by the addition of the polymeric flocculent (b). Alternatively, the
aqueous slurry of par-
10 ticulate material may be treated by the addition of the whole treatment
system followed by sub-
jecting the so treated aqueous slurry to a mixing stage. Nevertheless, it may
be desirable that
the aqueous slurry of particulate material is subjected to a mixing stage
after the addition of
each of the ionic polymeric de-coagulant (a) and the polymeric flocculent (b)
of the treatment
system. Optionally, cationic coagulant (c) may be added between the addition
of the ionic poly-
15 meric de-coagulant (a) and the polymeric flocculent (b), simultaneously
with the addition of the
polymeric flocculent (b) or subsequent to the addition of the polymeric
flocculent (b).
The ionic polymeric de-coagulant (a) may be added as an aqueous solution or as
dry particles
to the aqueous slurry.
Typically, the ionic polymeric de-coagulant is manufactured directly as an
aqueous solution, or it
20 may be in the form of dry particles and then pre-dissolved in water to
prepare an aqueous solu-
tion. In the latter case, generally the solid particulate ionic polymeric de-
coagulant, for instance
in the form of powder, beads or substantially spherical particles, may be
dispersed in water and
allowed to dissolve with agitation. This may be achieved using suitable make-
up equipment (as
described below regarding flocculent (b)). It is also possible that the ionic
polymeric de-
25 coagulant is manufactured directly as an aqueous solution of higher
concentration, and then
diluted with water and mixing to form a lower concentration aqueous solution.
The concentration of the aqueous solution of the ionic polymeric de-coagulant
(a) may be any
suitable concentration which would facilitate the ionic polymeric de-coagulant
solution to be fed
into and to mix with the aqueous slurry. Although it is conceivable that the
aqueous ionic poly-
30 meric de-coagulant concentration solution may be 60% weight/volume or
higher, it is usual that
the concentration be lower than 60% weight/volume. Usually the ionic polymeric
de-coagulant
solution will be from 0.1% to 50% weight/volume. Suitably, the aqueous ionic
polymeric de-
coagulant solution concentration will be from 1% to 40%, often from 5% to 25%.
The flocculent (b) may be added as an aqueous solution or as dry particles
directly to the ague-
ous slurry.
The aqueous solution of flocculent (b) is typically obtained by dissolving the
polymer in water or
by diluting a more concentrated solution of the polymer. Generally solid
particulate polymer, for
instance in the form of powder, beads or substantially spherical particles, is
dispersed in water
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and allowed to dissolve with agitation. This may be achieved using
conventional make up
equipment. Desirably, the polymer solution can be prepared using the Auto Jet
Wet (trade-
mark) supplied by BASF, for example as described in GB 1501938. The polymer
solution may
also be prepared according to any of the disclosures of US 4518261, US
5857773, US
6039470, US 5580168, US 5540499, US 5164429, US 5344619. The polymer solution
may
even be prepared using polymer slicing/shearing equipment, for instance as
described by US
4529794, US 4874588, or even any of the disclosures CA 2667277, CA 2667281, CA
2700239,
CA 2700244, CA 2775168, CA 2787175, CA 2821558 or US 2009/095688.
Alternatively, the
polymer may be supplied in the form of a reverse phase emulsion or dispersion
which can then
be inverted into water by conventional techniques.
The concentration of the aqueous solution of the polymer of flocculent (b) may
be any suitable
concentration which would facilitate the polymer solution to be fed into and
mix with the aque-
ous slurry. Although it is conceivable that the aqueous polymer solution may
be 5%
weight/volume or more, it is usual that the concentration be less than 5%
weight/volume. Typi-
cally, the polymer solution will tend to be below 3% weight/volume. Usually
the aqueous poly-
mer concentration will be at least 0.01% weight/volume. Suitably the aqueous
polymer concen-
tration may be from 0.01% to 5% weight/volume, typically from 0.02% to 3%,
often from 0.05%
to 1%.
The polymeric cationic coagulant (c) may be added as an aqueous solution or as
dry particles to
the aqueous slurry.
Typically, the cationic coagulant is manufactured directly as an aqueous
solution, or it may be in
the form of dry particles and then pre-dissolved in water to prepare an
aqueous solution. In the
latter case, generally the solid particulate cationic coagulant, for instance
in the form of powder,
beads or substantially spherical particles, can be dispersed in water and
allowed to dissolve
with agitation. This may be achieved using suitable make-up equipment (as
described above in
regard to flocculent (b)) It is also possible that the cationic coagulant is
manufactured directly as
an aqueous solution of higher concentration, and then diluted with water and
mixing to form a
lower concentration aqueous solution.
The concentration of the aqueous solution of the cationic coagulant (c) may be
any suitable
concentration which would facilitate the ionic polymeric de-coagulant solution
to be fed into and
to mix with the aqueous slurry. Although it is conceivable that the aqueous
cationic coagulant
concentration solution may be greater than 50% weight/volume, it is usual that
the concentra-
tion be equal to or lower than 50% weight/volume. Usually the cationic
coagulant solution will be
from 0.01% to 50% weight/volume. Suitably, the aqueous cationic coagulant
solution concentra-
tion will be from 0.1% to 30%, often from 1 to 10%.
The examples that follow are intended to illustrate the invention without in
any way being limit-
ing.
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Examples
Description of additives used in the examples
Ionic Polymeric De-coagulants Products 1-6
Product 1 is the terpolymer of vinyloxybutyl polyethylene glycol (adduct of
129 moles of eth-
ylene oxide with 4-hydroxy butyl mono vinyl ether) with acrylic acid and
maleic anhydride. The
molar ratio of these monomers is 1/4/0.6 and the weight average molar mass
approximately
53,500 g/mole. The preparation of the polymer was as described in US
2012/0035301 on page
4 under heading Polymer 1.
Product 2 is a copolymer of sodium acrylate and acrylamide in a weight ratio
of 75/25 weight %
having a weight average molecular weight of about 1 million Da and a charge
density of about 8
mmol/g in the form of a bead and prepared by a traditional reverse-phase
suspension polymeri-
sation process.
Product 3 is a homopolymer of sodium acrylate having a weight average
molecular weight of
about 5000 Da and a charge density of about 10.6 mmol/g. The product is in the
form of an
aqueous solution of concentration 40 % by weight and prepared as an aqueous
solution
polymerisation of sodium acrylate in the presence of chain transfer agent.
Product 4 is a copolymer of 80/20 weight % sodium acrylate and sodium salt of
ATBS (2-
acrylamido-2-methyl propane sulphonic acid) of weight average molecular weight
of about 5000
Da and charge density of about 9.5 mmol/g. The product is in the form of an
aqueous solution of
concentration 40 % by weight and prepared as an aqueous solution
polymerisation of sodium
acrylate in the presence of chain transfer agent.
Product 5 is a sulphonated melamine formaldehyde (SMF) polycondensate having a
theoretical
charge density of 3.5 mmol/g based on a repeating unit of 284 g/mol. The
weight average mo-
lecular weight is below 100,000 Da!tons. This SMF was synthesised according to
the general
procedure given in US 6555683. The molar ratio of melamine formaldehyde to
sodium hydrogen
sulphite was 1:3.19:1.53
Product 6 is a copolymer of vinyloxy butyl polyethylene glycol and acrylic
acid. The preparation
of this copolymer involves the copolymerisation of vinyloxy butyl polyethylene
glycol and acrylic
acid in an analogous procedure to Preparation Example 3 in EP 1902085 with the
exception
that a higher amount of acrylic acid was used (0.468 mole acrylic acid). The
molecular weight is
about 50,000 Da and the molar ratio of vinyloxy butyl polyethylene glycol to
acrylic acid was
1:7.8. The vinyloxy butyl polyethylene glycol was a polyethylene glycol-5800-
mono vinyl ether.
Flocculants 1-3
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Flocculant 1 is a copolymer of calcium diacrylate and acrylamide having a
weight ratio of 40/60
and exhibiting an intrinsic viscosity of 15 dl/g in the form of a powder and
prepared according to
W02017084986.
Flocculant 2 is a copolymer of sodium acrylate and acrylamide having a weight
ratio of 40/60
and exhibiting an intrinsic viscosity of 20 dl/g and in the form of a powder
prepared by standard
solution polymerisation to provide a gel which is cut and dried and then
ground to form the pow-
der.
Flocculant 3 is a copolymer of sodium acrylate and acrylamide having a weight
ratio of 40/60
and exhibiting an intrinsic viscosity of 10 dl/g and in the form of a bead
having been prepared by
traditional reverse-phase suspension polymerisation.
Coagulant
Coagulant 1 is the homopolymer of diallyl dimethyl ammonium chloride (DADMAC)
exhibiting an
intrinsic viscosity of 1.0 dl/g in the form of a bead and prepared by
traditional reverse-phase
suspension polymerisation.
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Example 1 ¨ Treatment of tailings from an oilsands, bitumen extraction
process.
Oi!sands process water, as used below, typically has a similar chemical
composition to the
aqueous phase of the MFT slurry used to prepared the test substrate.
A substrate sample with 1:1 SFR (sand/fines ratio) was prepared by blending
220 parts (wt) of
MFT, 81 parts (wt) of wet coarse tailings and 5 parts (wt) of oilsands process
water to yield a
combined tailings material (CbT) of the following composition:
Sand (particulates > 44 pm) 24.6 % wt
Fines (particulates <44 pm) 25.4 % wt
Process Water 50.0 % wt
.. The combined tailings material (CbT) was mixed continuously to ensure
homogeneity, and sub-
sampled into individual aliquots (50 g) for subsequent testing. Note, as both
the MFT and the
coarse tailings contain a small proportion of sands and fines respectively,
the final calculation of
the SFR (above) is adjusted to include sand and fines from both materials.
Part A ¨ testing for substrate dewaterability and consolidation:
De-coagulant solution, Product 1 was prepared to contain 0.5 %wt/vol of
polymer in oilsands
process water. Flocculent 1 solution was prepared to contain 0.5 %wt/vol of
polymer in oilsands
process water.
The 50 g aliquot of the combined tailings substrate (CbT) is placed in a 120
ml beaker and
mixed with a flat blade stirrer at 400 rpm. After 10 seconds, the required
amount of Product 1
solution is added and subsequently, after 10 seconds, the required amount of
flocculent solution
is added, and mixing is continued until the sample is conditioned to the
visual point of optimum
flocculation / net water release (NWR), at which time the mixer is stopped.
The mixing time after
the flocculent addition required to reach the point of optimum conditioning is
recorded, and it
may differ significantly for different types and dosages of de-coagulant and
flocculent.
After conditioning, the treated substrate is transferred into a pressure
filter apparatus consisting
of a cylindrical chamber of diameter 3.25 cm, fitted with fine filter media at
one end, and a solid
sliding piston at the other. (see Figure 2). A force equal to an internal
pressure of 6 psi is then
applied to the piston for a period of 10 mins, during which the water expelled
through the filter
media is collected. The particulate solids content of the release water was
determined
gravimetrically by drying at 110 C for 2 hrs. The dry weight value obtained
was adjusted for the
electrolyte content of the process water (0.27 %wt/vol). The moisture content
of the filtercake
was determined by drying at 110 C for 24 hours.
Part B ¨ testing for fines capture during sub-aqueous deposition
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50 g aliquot of the combined tailings substrate (CbT) is treated with de-
coagulant and flocculant
as has been previously described in Part A. After conditioning, the treated
substrate is
transferred into a 250 ml measuring cylinder which already contains 200 ml of
water. The
cylinder is then inverted vigorously three times to disperse the treated
substrate into the bulk of
5 the water. The cylinder is then left to stand for 10 mins before sampling
the supernatant water
and measuring the residual turbidity.
Table 1: (See Figures 3 - 5)
Part A Part B
Product 1 Flocculant 1 Cake Filtrate
Mixing Mixing
Turbidity
Dose (g/t) Dose (g/t) Moisture Solids
Time (s) (%wt) (%wt) Time (s)
(NTU)
0 800 22.2 45.9 1.16 24.1
1214
50 800 22.1 46.7 1.15 29.6 838
100 800 27.1 40.5 0.98 32.5 252
150 800 24.8 40.7 0.97 27.7 579
200 800 27.3 41.6 0.70 35.3 331
240 800 31.3 36.0 0.67 31.3 321
280 800 30.9 34.2 0.76 33.1 323
The results show that for the substrate mixture with a 1:1 SFR, the addition
of Product 1
significantly reduced the residual moisture in the dewatered solids, and
improved the retention
10 and capture of fine particles during both dewatering and sub-aqueous
deposition.
Example 2 - Treatment of tailings from an oilsands, bitumen extraction process
Testing was carried out as previously described in example 1 above except that
a substrate
sample with 1.75:1 SFR (sand/fines ratio) was prepared by blending 57 parts
(wt) of MFT, 42
parts (wt) of wet coarse tailings and 20 parts (wt) of oilsands process water
to yield a combined
15 tailings material (CbT) of the following composition:
Sand (particulates >44 pm) 31.8 %wt
Fines (particulates <44 pm) 18.2 %wt
Process Water 50.0 %wt
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Table 2: (See Figures 6 - 8)
Part A Part B
Product 1 Flocculent 1 Cake Filtrate
Mixing Mixing
Turbidity
Dose (g/t) Dose (g/t) Moisture Solids
Time (s) (%wt) (%wt) Time (s)
(NTU)
0 360 12.3 37.3 2.10 12.3
2812
50 360 11.9 25.0 1.19 11.3
2080
100 360 11.7 25.7 1.24 11.9
2170
150 360 11.7 29.7 1.32 12.6
1690
200 360 14.9 23.9 0.92 12.0 954
240 360 14.5 23.7 0.85 12.0 713
280 360 14.4 26.4 0.86 12.5 380
0 400 12.0 34.5 1.41 14.4
1600
200 400 15.9 24.9 0.84 15.8 339
The results show that for the substrate mixture with a 1.75:1 SFR, the
addition of Product 1
significantly reduced the residual moisture in the dewatered solids, and
improved the retention
and capture of fine particles during both dewatering and sub-aqueous
deposition. The
combination dosage of 50 g/t Product 1 with 360 g/t flocculent also achieved
significantly better
results than 400 g/t flocculent alone. For example, the residual cake moisture
was only 25 % for
the combination, whereas the similar dose of flocculent alone had a residual
cake moisture of
34.5 %.
Example 3 - Treatment of tailings from an oilsands, bitumen extraction process
Testing was carried out as previously described in example 1 above except that
a substrate
sample with 3:1 SFR (sand/fines ratio) was prepared by blending 60 parts (wt)
of MFT, 88 parts
(wt) of wet coarse tailings and 60 parts (wt) of oilsands process water to
yield a combined
tailings material (CbT) of the following composition:
Sand (particulates > 44 pm) 37.5 %wt
Fines (particulates <44 pm) 12.5 %wt
Process Water 50.0 %wt
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Table 3: (See Figures 9 - 11)
Part A Part B
Product 1 Flocculant 1 Cake Filtrate
Mixing Mixing
Turbidity
Dose (g/t) Dose (g/t) Time (s) Moisture Solids
(%wt) (%wt) Time (s)
(NTU)
0 150 8.8 32.6 3.64 7.2
6047
50 150 9.1 32.2 2.75 8.6
4750
100 150 9.1 23.9 1.68 9.1
5390
150 150 8.1 22.8 1.11 8.1
3230
200 150 10.8 29.4 1.06 9.6
1740
240 150 12.3 28.3 1.05 6.6
1160
280 150 9.2 23.8 0.68 5.9 572
The results show that for the substrate mixture with a 3:1 SFR, the addition
of Product 1
reduced the residual moisture in the dewatered solids and improved the
retention and capture
of fine particles during both dewatering and sub-aqueous deposition.
Example 4 - Treatment of tailings from an oilsands, bitumen extraction process
Testing was carried out as previously described in example 2 above using the
substrate sample
with 1.75:1 SFR (sand/fines ratio). A number of different de-coagulant and
flocculant chemistry
combinations were tested.
Table 4:
Product Flocculant Part A Part B
Cake Filtrate
Dose Dose Mixing Mixing
Turbidity
# # Moisture Solids
(g/t) (g/t) Time (s) (%wt) (%wt) Time (s) (NTU)
n/a 0 2 360 37.1 47.9 2.04 43.8
6982
1 200 2 360 36.5 34.1 1.49 34.3
2948
n/a 0 1 360 12.3 37.3 2.10 12.3
2812
2 100 1 360 17.1 24.9 0.67 11.2
147
2 200 1 360 15.0 23.7 0.54 12.3
253
3 50 1 360 15.1 44.3 1.17 13.0
568
4 40 1 360 12.0 42.6 1.33 12.2
619
4 96 1 360 15.0 51.2 0.12 NT
NT
5 100 1 360 11.8 40.0 2.77 9.5
1793
5 200 1 360 12.0 39.0 2.49 11.3
2580
6 100 1 360 11.8 39.1 1.92 9.7
2027
6 200 1 360 12.0 31.0 1.20 10.6
1042
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The results show that in all cases the addition of the de-coagulant products
improved the fines
solids capture in the sub-aqueous deposition test compared to the
corresponding treatment with
flocculant alone. Products 1 and 2 are particular effective in improving both
the dewatering and
fines capture. Although de-coagulants with very high anionic charge densities,
such as Product
.. 3, 4 and 5 were effective they were not as effective as Products 1 and 2,
especially in respect to
facilitating the rapid separation of water from the solids. Product 6 improved
dewatering and
fines capture at lower doses. Fines capture was improved at greater doses of
Product 6.
Example 5 ¨ treatment of tailings from an oilsands, bitumen extraction process
Testing was carried out as previously described in example 2 above using the
substrate sample
with 1.75:1 SFR (sand/fines ratio). The effect of adding a coagulant, in the
form of a 0.5%
wt/vol solution in process water, after the flocculation step, was evaluated.
Table 5:
Product 1 Cake Filtrate
Flocculant 1 Coagulant 1 Mixing Mixing
Turbidity
Dose Moisture Solids
(g/t)
Dose (g/t) Dose (g/t) Time (s) (%wt)
(%wt) Time (s) (NTU)
100 360 0 11.7 25.7 1.24 11.9
2170
100 360 100 10.8 24.9 0.42 12.4
299
200 360 0 14.9 23.9 0.92 12.0
954
200 360 100 12.0 22.6 0.15 11.1
44
The results show that the further addition of a coagulant may be beneficial to
further improve
the fine capture and retention during the dewatering of the substrate.
Example 6
Testing was carried out as previously described in example 1 above except that
a substrate
sample with 1.6:1 SFR (sand/fines ratio) was prepared by blending 200 parts
(wt) of MFT, 110
parts (wt) of wet coarse tailings to yield a combined tailings material (CbT)
of the following
composition:
Sand (particulates > 44 pm) 34.5 %wt
Fines (particulates <44 pm) 21.5 %wt
Process Water 44.0 %wt
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Table 6: (See Figures 12¨ 13)
Part A Part B
Product 1 Flocculant 3 Cake Filtrate
Mixing Mixing
Turbidity
Dose (g/t) Dose (g/t) Moisture Solids
Time (s) (%wt) (%wt) Time (s)
(NTU)
0 715 42.9 44.8 NT 46.0
1020
36 715 46.4 36.6 NT 47.0 804
71 715 51.1 32.5 NT 45.1 448
107 715 46.8 32.9 NT 42.8 181
143 715 45.0 26.0 NT 45.5 224
179 715 49.4 24.3 NT 43.7 61
214 715 56.9 24.7 NT 55.0 65
The results show that for the substrate mixture with a 1.6:1 SFR, the addition
of Product 1
reduced the residual moisture in the dewatered solids and improved the
retention and capture
of fine particles during both dewatering and sub-aqueous deposition.
