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Patent 3127837 Summary

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(12) Patent: (11) CA 3127837
(54) English Title: SYSTEMS AND METHODS FOR REDUCING THE PARTICULATE CONTENT OF A LIQUID-PARTICULATE MIXTURE
(54) French Title: SYSTEMES ET PROCEDES DE REDUCTION DE LA TENEUR EN MATIERES PARTICULAIRES D'UN MELANGE LIQUIDE-PARTICULAIRE
Status: Granted
Bibliographic Data
(51) International Patent Classification (IPC):
  • B01D 21/26 (2006.01)
  • B01D 45/12 (2006.01)
  • B01J 2/04 (2006.01)
  • B07B 7/08 (2006.01)
(72) Inventors :
  • COBOS URDANETA, SYGIFREDO (Canada)
(73) Owners :
  • ENOVIST INC. (Canada)
(71) Applicants :
  • ENOVIST INC. (Canada)
(74) Agent:
(74) Associate agent:
(45) Issued: 2022-03-08
(86) PCT Filing Date: 2020-02-04
(87) Open to Public Inspection: 2020-08-13
Examination requested: 2021-08-23
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/CA2020/050130
(87) International Publication Number: WO2020/160648
(85) National Entry: 2021-07-26

(30) Application Priority Data:
Application No. Country/Territory Date
62/800,832 United States of America 2019-02-04

Abstracts

English Abstract

An apparatus and method for reducing the particulate content of a liquid-particulate mixture. The apparatus has an atomiser and a gas-flow classifier. The atomiser receives the liquid-particulate mixture and atomises it. The gas-flow classifier receives the atomised liquid-particulate mixture from the atomiser and directs each atomised particle through a gas towards one of two classifier outlets based on the liquid-solids ratio of the particles.


French Abstract

L'invention concerne un appareil et un procédé pour réduire la teneur en particules d'un mélange liquide-particulaire. L'appareil comprend un atomiseur et un classificateur d'écoulement de gaz. L'atomiseur reçoit le mélange liquide-particulaire et l'atomise. Le classificateur de l'écoulement de gaz reçoit le mélange liquide-particulaire atomisé de l'atomiseur et dirige chaque particule atomisée à travers un gaz vers l'une des deux sorties de classificateur sur la base du rapport liquide-solides des particules.

Claims

Note: Claims are shown in the official language in which they were submitted.


CLAIMS
1. An apparatus for reducing the particulate content of a liquid-
particulate mixture
comprising a liquid and solids, the apparatus comprising:
an atomiser, the atomiser configured to receive the liquid-particulate mixture
and to
atomise the liquid-particulate mixture into particles, each particle having a
particular liquid-solids
ratio; and
a gas-flow classifier configured to receive the atomised liquid-particulate
mixture,
wherein
the gas-flow classifier comprises:
a gas chamber configured to direct individual atomised particles through a gas

along different trajectories based on the liquid-solids ratio of the
particles;
a reduced-solids outlet configured to receive particles following a trajectory

associated with a higher liquid-solids ratio; and
a reduced-liquid outlet configured to receive particles following a trajectory

associated with a lower liquid-solids ratio.
2. The apparatus of claim 1, wherein the atomiser is configured to eject
the liquid-
particulate mixture in a co-current with a surrounding air stream that
atomises the liquid-
particulate mixture into particles.
3. The apparatus according to any one of claims 1-2, wherein the atomiser
is configured to
receive a pre-existing gas stream containing the liquid-particulate mixture,
and to further
disperse the liquid-particulate mixture into smaller particles.
4. The apparatus according to any one of claims 1-3, wherein the gas-flow
classifier
comprises a cyclone.
5. The apparatus according to any one of claims 1-4, wherein the atomiser
comprises an
atomising nozzle.
6. The apparatus according to any one of claims 1-5, wherein the atomiser
is configured to
use centrifugal forces to atomise the liquid-particulate mixture.
7. The apparatus according to any one of claims 1-6, wherein the atomiser
is configured to
use ultrasound to atomise the liquid-particulate mixture.
8. The apparatus according to any one of claims 1-7, wherein the apparatus
comprises a
gas pump configured to generate gas flow within the gas chamber.
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9. The apparatus according to claim 8, wherein the gas pump is configured
to generate gas
flow within the gas chamber by drawing air out from one of the classifier
outlets.
10. The apparatus according to any one of claims 1-9, wherein the apparatus
comprises
more than two classifier outlets.
11. The apparatus according to any one of claims 1-10, wherein one of the
classifier outlets
is towards the top of the gas chamber and the other classifier outlet is
towards the bottom of the
gas chamber.
12. The apparatus according to any one of claims 1-11, wherein the atomiser
and gas-flow
classifier are configured to operate at a temperature below the boiling point
of the liquid in the
liquid-particulate mixture.
13. The apparatus according to any one of claims 1-12, wherein the
configuration of at least
one of the outlets and the atomiser is adjustable to control the liquid-solids
ratios of the
received particles.
14. The apparatus according to any one of claims 1-13, wherein the
apparatus comprises a
dredge for extracting the liquid-particulate mixture from a tailings pond.
15. The apparatus according to any one of claims 1-14, wherein the
apparatus comprises a
screen for removing particulates exceeding a threshold size before being
atomised by the
atomiser.
16. The apparatus according to any one of claims 1-15, wherein the
apparatus comprises a
feed pump configured to pump the liquid-particulate mixture to the atomiser.
17. The apparatus according to any one of claims 1-16, wherein the atomiser
configured to
co-flow the liquid-particulate mixture with a stream of air to atomise the
liquid-particulate mixture
into particles.
18. The apparatus according to any one of claims 1-17, wherein the atomiser
is configured
to generate a particle distribution with a volume average particle size, Dv50,
of between 0.5-40
microns.
19. The apparatus according to any one of claims 1-18, wherein the atomiser
is configured
to generate a particle distribution with a volumetric 90% particle size, Dv90,
of less than 100
microns.
20. A method of reducing the particulate content of a liquid-particulate
mixture comprising a
liquid and solids, the method comprising:
29
Date Recue/Date Received 2021-11-10

receiving the liquid-particulate mixture;
atomising the liquid-particulate mixture;
directing individual atomised particles through a gas chamber of a gas-flow
classifier
towards one of two classifier outlets based on the liquid-solids ratio of the
particles, the two
classifier outlets comprising:
a reduced-solids outlet configured to receive particles following a trajectory
associated
with a higher liquid-solids ratio; and
a reduced-liquid outlet configured to receive particles following a trajectory
associated
with a lower liquid-solids ratio.
21. The method of claim 20, wherein the liquid-particulate mixture is
extracted from a tailings
pond.
22. The method according to any one of claims 20-21, wherein the pressure
in the gas
chamber is above the vapor pressure of the liquid.
23. The method according to any one of claims 20-22, wherein the liquid is
water.
24. The method according to any one of claims 20-23, wherein the atomizing
and the
directing of the individual atomised particles through the gas chamber occur
at a temperature
below the boiling point of the liquid in the liquid-particulate mixture.
25. The method according to any one of claims 20-24, wherein the liquid-
particulate mixture
comprises multiple liquids.
Date Recue/Date Received 2021-11-10

Description

Note: Descriptions are shown in the official language in which they were submitted.


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Systems and Methods for Reducing the Particulate Content of
a Liquid-Particulate Mixture
FIELD OF THE INVENTION
[0001] The invention relates to reducing the particulate content of a liquid-
particulate
mixture. In particular, the invention relates to the dewatering of mature and
fluid fine
tailings.
BACKGROUND
[0002] Oil sands (e.g. in Alberta, Canada) is a mixture of bitumen, mineral
matter and
water in varying proportions. Bitumen content may be from 0 to 19 wt. %,
averaging
12 wt. %, water is between 3-6 wt. %, typically increasing as bitumen content
decreases. Mineral content, (predominantly quartz, silts and clay) may be
between 84-
86 wt. %. The major clay mineral components are in the region are 40-70 wt. %
kaolinite, 28-45 wt. % illite and 1-15 wt. % montmorillonite.
[0003] Oil sands bitumen surface mining extraction may be based on the Clark
Hot
Water Extraction Process (CHWE). Oil sands are mined by trucks and shovels,
digested at the extraction plant, and conditioned in large tumblers with the
addition of
hot water, steam, and NaOH. The CHWE process achieves over 90% bitumen
recovery efficiency at about 85 C and pH of 8.5.
[0004] In the commercial oil sands operations using CHWE, while bitumen is
separated through the top of separation units using air flotation, a bottom
stream of the
process is produced and known as tailings. The coarse tailings effluent, which
is called
"whole tailings", is in the form of a slurry, and it is a mixture of sand
particles, dispersed
fines, water, and residual bitumen. It typically has about 55 wt. % solid
content, of
which 82 wt. % is sand, 17 wt. % is fines smaller than 44 pm, and 1 wt. % is
residual
bitumen. The whole tailings are either discharged directly into a storage
facility or
classified through a cyclone separator and thickener before being discharged
into the
tailings pond.
[0005] In a conventional tailings deposition, the whole tailings are pumped
into large
tailings ponds. Here, the coarse particles settle out to form dykes and
beaches, while
much of the fines and residual bitumen flow into the pond as a thin and
immature fine
tailings stream at approximately 8% solid content (Jeeravipoolvarn, 2005 ¨ see
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Bibliography below for full citations). After a few (e.g. 3) years, the fines
settle to 30%-
35% solid content and are referred to as mature fine tailings (MFTs).
[0006] Mature fine tailings (MFT) is generally a mixture of residual bitumen,
sand, silt,
fine clay particles and water. The clay content (% by dry mass of fine)
typically varies
from 30-50% percent, and the solid content generally ranges from 30 to 35%.
[0007] MFT is a strong suspension, created as a result of different chemical
and
physical properties (Chalaturnyk et. al, 2002) such as:
1. Water-soluble asphaltic acids that remain in the tailings due to the
residual
bitumen. This material will decrease the surface and interfacial tension of
the
water and acts as a clay dispersant.
2. Ultrafine clay particles (less than 0.2 pm) that retain large amounts of
water by
forming a gel like structure within the MFT. It is usually stated water is
"entrapped" within this micropore structure.
3. A strong "house of cards" clay structure may be created based on the
existence
of organic material on the surface of the clay particles.
[0008] Investigations on MFT micropore structure done by Tang (Thesis,
University of
Alberta, 1997) captured the microstructure of the raw MFT, confirming that MFT
had
typically a 'card-house' structure with large pore spaces entrapping bulk of
water. Other
work (Roshani thesis, University of Ottawa, 2017), shows the pore diameter of
the
micro pore structure in raw MFTs after left to dry in ambient conditions,
where the micro
pore structure of the system is unaffected. The pore diameter was found to be
mostly
between 0.1 to 70 pm.
[0009] The fact that mature fine tailings behave as a colloidal fluid and have
very slow
consolidation rates significantly limits options to reclaim tailings ponds.
Without
dewatering or solidifying the mature fine tailings, tailings ponds can have
increasing
economic and environmental implications over time.
[0010] There are some methods that have been proposed for disposing of or
reclaiming oil sand tailings by attempting to solidify or dewater mature fine
tailings. If
mature fine tailings can be sufficiently dewatered so as to convert the waste
product
into a reclaimed firm terrain, then many of the problems associated with this
material
can be curtailed or completely avoided. As a general guideline target,
achieving a
solids content higher than 65 wt. % for mature fine tailings is considered
sufficiently
"dried" for reclamation.
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[0011] One known method for dewatering MFT involves a freeze-thaw approach.
MFT
is deposited into small, shallow pits that are allowed to freeze over the
winter and
undergo thawing and evaporative dewatering the following summer. Scale up of
such
a method requires enormous surface areas and is highly dependent on weather,
climate and seasons.
[0012] Some other known methods have attempted to treat MFT with the addition
of
a chemical to create a thickened paste that will solidify or eventually
dewater.
[0013] One such method, referred to as "consolidated tailings" (CT), involves
combining mature fine tailings with sand and gypsum. A typical consolidated
tailings
mixture is about 60 wt. % mineral (balance is process water) with a sand to
fines ratio
of about 4 to 1, and 600 to 1000 ppm of gypsum. This combination can result in
a non-
segregating mixture when deposited into the tailings ponds for consolidation.
However,
the CT method has a number of drawbacks. It relies on continuous extraction
operations for a supply of sand, gypsum and process water. The blend must be
tightly
controlled. Also, when consolidated tailings mixtures are less than 60 wt. %
mineral,
the material segregates with a portion of the fines returned to the pond for
reprocessing
when settled as mature fine tailings. Furthermore, the geotechnical strength
of the
deposited consolidated tailings requires containment dykes and, therefore, the
sand
required in CT competes with sand used for dyke construction until extraction
operations cease. Without sand, the CT method cannot treat mature fine
tailings.
[0014] Some other methods have attempted to use polymers or other chemicals to

help dewater MFT. These methods involve the mixing of flocculant polymer
solutions
with the MFT fluids. This is not a straightforward process and adds
considerable cost
to the treatment of MFTs. A current process uses centrifuging of thickened
MFTs with
polymer flocculants. The flocculants increase the particle size by aggregating
"flocs",
which due to a larger particle size can be separated more efficiently in a
decanter
centrifuge. However, the operation depends completely on the preparation of
polymer
solutions, which depend on the use of polymer slicing and hydration units.
[0015] Additionally, the consumption of polymer is at rates of 1000 grammes of

polymer per ton of solids, which translate in high operating costs for
processing. In
addition, at concentrations of polymer solutions that reach 0.4%, these high
molecular
weight polymer molecules (usually MW > 5 MM Da, and up to 20 MM Da), may
produce
very viscous (p > 500 cP) solutions and many of them exhibit viscoelastic
behavior.
The mixing involved to prepare this polymer also adds to operating energy
costs, as
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does the mixing of the polymer solutions with the MFTs and pumping the
resulting
viscous fluids. Finally, the centrifuging of such fluids withdraws
considerably more
energy, at least between 40 to 50 KJ/I for such viscous fluids.
[0016] Previous technology for separating phases of matter have been based on
spray
evaporation and/or spray drying principles. These methods use atomisation to
increase the surface area of the dispersed phase, which is a liquid, with the
purpose
of considerably increasing the rate of heat transfer to the liquid phase in
order to
vaporize it more efficiently.
[0017] CA 2,805,804 (Van Der Merwe et al.) discloses a tailings solvent
recovery unit
(TSRU) which includes a separation apparatus receiving solvent diluted
tailings and
producing solvent component and solvent recovered tailings component. The
separation apparatus includes a flash vessel, a tailings outlet, a solvent
outlet, and an
inlet spray system including multiple nozzles arranged around a periphery of
the side
walls of the flash vessel sized and configured and extending within the
flashing
chamber for subjecting the solvent diluted tailings to flash-atomisation to
form a spray
of droplets distributed over the cross-section of the vessel.
[0018] US 4,944,845 (Bartholic) discloses an apparatus for the treatment of a
liquid
hydrocarbon charge containing solids or solids-forming contaminants, e.g.,
inorganic
solids, metals and asphaltenes, which includes a contactor vessel having a
liquid
charge inlet, a vaporizing media inlet above the charge inlet and a vapor-
solids outlet.
An atomiser is positioned in the charge inlet for forming small particles of
the liquid
charge and directing the particles of liquid in a substantially horizontal
flat pattern into
the contactor vessel. The vapor-solids-outlet is positioned in the contactor
vessel
substantially opposite the liquid charge inlet to receive product vapors and
entrain solid
particles and rapidly pass the same into cyclones connected to the vapor-
solids-outlet
for separating solid particles from product vapors. A stripper vessel is
located beneath
the contactor vessel for receiving heavy solid particles.
[0019] US 6,669,104 (Koveal et al.) discloses a liquid atomisation process
comprising
forming a two-phase fluid mixture of a liquid and a gas, under pressure,
dividing the
fluid into two separate streams which are passed into and through an
impingement
mixing zone in which they are impingement mixed to form a single stream of two-
phase
fluid. The mixed, single stream is then passed into and through a shear mixing
zone
and then into a lower pressure expansion zone, in which atomisation occurs to
form a
spray of atomised drops of the liquid. The impingement and shear mixing zones
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comprise respective upstream and downstream portions of a single fluid
passageway
in a nozzle. This is useful for atomising (and boiling/vaporizing) the hot
feed oil in a
fluid catalytic cracking (FCC) process.
SUMMARY
[0020] In accordance with the invention, there is provided an apparatus for
reducing
the particulate content of a liquid-particulate mixture, the apparatus
comprising:
an atomiser, the atomiser configured to receive the liquid-particulate mixture

and to atomise the liquid-particulate mixture into particles, each particle
having a
particular liquid-solids ratio; and
a gas-flow classifier configured to receive the atomised liquid-particulate
mixture, wherein the gas-flow classifier comprises:
a gas chamber configured to direct individual atomised particles
through a gas along different trajectories based on the liquid-solids ratio of
the
particles;
a reduced-solids outlet configured to receive particles following a
trajectory associated with a higher liquid-solids ratio; and
a reduced-liquid outlet configured to receive particles following a
trajectory associated with a lower liquid-solids ratio.
[0021] In the context of this disclosure, particulates are solids whereas
particles may
comprise solids and/or liquids.
[0022] The atomiser may be configured to receive a pre-existing gas stream
containing a liquid-particulate mixture, wherein the atomiser is configured to
further
disperse the liquids-particulates into smaller particles (e.g. relative to the
particles
present in the pre-existing gas stream received by the atomiser), each
particle having
a particular liquid-solids ratio.
[0023] The atomiser (or atomisation device) may be configured to eject the
liquid-
particulate mixture in a co-current with a surrounding air stream that
atomises the
liquid-particulate mixture into particles, each particle having a particular
liquid-solids
ratio.
[0024] It will be appreciated that liquid-solids ratio may affect the
trajectory due to
differences in one or more of the following: particle density; the shape of
the particle;
the size of the particle; and the deformability of the particle.
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[0025] The gas-flow classifier may comprise a cyclone.
[0026] The atomiser may comprise an atomising nozzle. The atomising nozzle may

be configured to generate a directed spray of particles. For example, the
nozzle may
be configured to produce a beam of particles. The nozzle may be configured
such that
the particles exit the nozzle with a spray angle from 350 to 165 . It will be
appreciated
that the classifier outlets may be shaped to correspond the symmetry of the
spray. For
example, if the nozzle is configured to generate a flat horizontal spray
pattern, one or
more of the outlets may also be configured to be a flat horizontal slot.
[0027] The atomiser may be configured to use centrifugal forces to atomise the
liquid-
particulate mixture. A rotary atomiser may comprise a rotating member (e.g.
cup or
disc). The liquid-particulate mixture may be projected towards the rotating
cup or disc,
the liquid being ejected in a spray of particles from the rim of the rotating
cup or disc.
It will be appreciated that the classifier outlets may be shaped to correspond
the
symmetry of the spray. For example, the reduced liquid outlet in a rotary
atomiser may
be in the form of a circular slot aligned with the edge of the rotating
member.
[0028] The atomiser may be configured to use ultrasound to atomise the liquid-
particulate mixture. Ultrasonic atomisation relies on an electromechanical
device that
vibrates at a very high frequency. Fluid passes over the vibrating surface and
the
vibration causes the fluid to break into droplets. Applications of this
technology may
include: drying liquids; powdered milk for example, in the food industry,
surface
coatings in the electronics industry. Ultrasonic atomisation technology may be

particularly effective for low-viscosity Newtonian fluids.
[0029] The apparatus may comprise a gas pump configured to generate gas flow
within the gas chamber.
[0030] The apparatus may comprise a gas pump configured to draw the liquids
into
the chamber, in such a way gas and liquids enter simultaneously into the
chamber,
with the air producing small particles of the fluid co-entering with the air.
[0031] The apparatus may comprise a gas pump configured to generate gas flow
within the gas chamber by drawing air out from one of the classifier outlets.
[0032] The apparatus may comprise more than two classifier outlets. The
apparatus
may comprise a reduced-solids outlet and a reduced-liquid outlet. The
apparatus may
comprise a reduced-solids outlet, a reduced-liquid outlet and an intermediate
outlet.
The liquid-particulate mixture from the intermediate outlet may be recycled
through the
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apparatus. The intermediate outlet may be configured to receive particles with
a liquid-
solids ratio (and/or density) between the liquid-solids ratio (and/or density)
of particles
directed towards the reduced-liquid outlet and the liquid-solids ratio (and/or
density) of
particles directed towards the reduced-solids outlet.
[0033] One of the classifier outlets may be positioned towards the top of the
gas
chamber and the other classifier outlet may be positioned towards the bottom
of the
gas chamber.
[0034] The atomiser and gas-flow classifier may be configured to operate at a
temperature below the boiling point of the liquid in the liquid-particulate
mixture. The
atomiser and gas-flow classifier may be configured to operate at ambient
temperature
(e.g. below 40 C). The atomiser and gas-flow classifier may be configured not
to heat
the liquid-particulate mixture.
[0035] To avoid cavitation, the pressure in the gas-flow classifier may be
configured
to be above the vapor pressure of the liquids.
[0036] At least one of the outlet configurations and the atomising nozzle
configuration
may be adjustable to control or adjust the liquid to solid ratios of the
reduced-solids
and liquid-reduced outputs. The apparatus may be configured such that the %
mass
of solids in the liquid-reduced output exceeds 65%. This would allow the
liquid-reduced
output to be considered reclaimed.
[0037] The apparatus may be configured to produce very fine particles/droplets
(e.g.
less than 100 microns). The Dv50 value of the particle size distribution may
be between
0.5-40 microns (e.g. 20 microns). The Dv90 value may be less than 100 microns
(e.g.
40 microns or less). Figure 7 shows an example of a target particle size
distribution.
[0038] The apparatus may comprise a dredge for extracting the liquid-
particulate
mixture from a tailings pond.
[0039] The apparatus may comprise a screen for removing particulates exceeding
a
threshold size before being atomised by the atomiser.
[0040] The apparatus may comprise a feed pump configured to pump the liquid-
particulate mixture to the atomiser.
[0041] A dewatering system may comprise multiple dewatering apparatus arranged
in
parallel and/or in series.
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[0042] According to a further aspect, there is provided a method of reducing
the
particulate content of a liquid-particulate mixture, the apparatus comprising:
receiving the liquid-particulate mixture;
atomising the liquid-particulate mixture;
directing individual atomised particles through a gas chamber of a gas-flow
classifier towards one of two classifier outlets based on the liquid-solids
ratio (and
density difference) of the particles.
[0043] The liquid-particulate mixture may be extracted from a tailings pond.
[0044] Atomisation refers to separating something into fine particles. When
applied to
liquids, it is the process of breaking up bulk liquids into droplets. In the
context of this
invention, atomised particles may be liquid droplets, solid particulates or a
mixture of
liquid and solid. The particulates may range in size between 0.1-100 pm.
[0045] The atomiser may be configured to produce a spray. A spray is generally

considered as a system of particles suspended in or travelling through a
continuous
gaseous phase.
[0046] Sprays may be produced in various ways. Some atomisers devices achieve
atomisation by creating a high velocity between the liquid and the surrounding
gas
(usually air). Pressure nozzles accomplish this by discharging the liquid at
high velocity
into quiescent or relatively slow-moving air. That is, nozzle atomisation
employs a
pump which pressurizes and forces the fluid through the orifice of a nozzle to
break
the liquid into fine droplets. The orifice size can typically range between
the range of
0.5 to 3 mm, and specifications depend on discharge pressure and flow rates.
The size
of the droplets depends on the size of the orifice and the pressure drop. A
larger
pressure drop across the orifice produces smaller droplets.
[0047] In order to estimate the immediate discharge flow rate from a given
nozzle
atomiser, the Bernoulli principle may be used under certain assumptions:
= the flow must be steady, i.e. the flow parameters (velocity, density,
etc...) at any
point cannot change with time,
= the flow must be incompressible ¨ even though pressure varies, the
density must
remain constant along a streamline;
= friction by viscous forces must be negligible.
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[0048] Based on the conservation of energy and under the above conditions, the

energy of the incompressible flow remains constant.
[0049] For the current application, there will be changes in the droplets
velocities after
the outlet, due to additional changes in the flow area, internal air flow
rates, drag forces
and the density of particles/droplets depending on the liquid/solids ratio.
[0050] Regarding the droplet size, pressure may be used to control the droplet
size.
For most nozzles the higher the fluid pressure generally the smaller the
droplet size.
For an hydraulic nozzle, the relationship between pressure and mean droplet
size may
typically be expressed as:
DI (PL
D2 P2
[0051] Where D1 is the mean droplet size at pressure 1(P1) and D2 is the mean
droplet size at pressure 2 (P2). This gives an approximate relationship for
comparing
droplet sizes for any given nozzle. The droplet size for a particular pressure
also
depends on the design of the nozzle.
[0052] Therefore, for hydraulic nozzles, to reduce the particle/droplet size
for a given
feed rate, a smaller orifice and a higher pump pressure may be employed.
[0053] Rotary atomisers are configured to eject liquid at high velocity from
the rim of
a rotating member (cup, disc or wheel). The rotating member breaks the liquid
stream
of slurry into droplets. The rotating member may be about 5 to 50 cm in
diameter, which
spins in the range of about 5,000 to 40,000 rpm. The size of the droplets
produced by
a centrifugal atomisation device is about inversely proportional to the
peripheral speed
of the disc or wheel. Therefore, the size of the droplet may be controlled by
controlling
the peripheral speed of the rotating member.
[0054] Another method of achieving a high relative velocity between liquid and
air is
to expose slow-moving liquid into a high-velocity stream of air. Devices based
on this
approach may also be known as air-assist, airblast or, more generally, twin-
fluid
atomisers.
[0055] Air atomising nozzles achieve very fine droplet size, and so may be
particularly
effective in the present technology. In addition, air atomising nozzles use
the impact of
compressed air onto the fluid to break it apart and form the spray pattern.
This may
help mitigate issues around blocking.
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[0056] In direct pressure nozzles the fluid is broken up (atomised) into
droplets by either
impact on a surface or by the shearing force caused by passing the liquid
through a shaped
orifice. In both cases the energy required for the atomisation comes from the
potential
energy of the fluid itself. Essentially the energy available for atomisation
is a function of
fluid pressure.
[0057] In air atomising nozzles, pressurised air (or other gas) is used to
impact upon the
fluid being sprayed. The impact of the gas causes the fluid to break apart
into a fine spray.
This means that the energy required for atomisation is no longer dependent on
fluid
pressure. Because of this, very fine sprays can be produced at low fluid
pressures. This
allows for very fine, low volume sprays to be delivered.
[0058] The level of atomisation for air atomising nozzles is not primarily a
function of
liquid pressure and pattern type (although these still do have some effect).
Rather it
is primarily dependent on the amount and velocity of air being used. The
higher the air
pressure and flow rate the smaller the droplets will be. This means that even
very low
flow rates at low fluid pressures can be finely atomised.
[0059] Air atomising nozzles are configured to produce very fine droplets and
so will
be low impact, but the reach of these fine sprays can be greatly enhanced with
the
presence of air. Hydraulic misting nozzles may absorb much of the internal
energy of
the fluid being sprayed to break it apart leaving little for projecting the
fluid forwards.
This means that fine sprays from hydraulic nozzles may have a lower forward
projection before they are classified by an air current.
[0060] In contrast, with air atomising nozzles, the compressed air from such
nozzles
can be used to help project even very fine spray over many metres. Therefore,
there
is then a compromise between the atomisation design, so that
droplets/particles lose
energy for the travel distance and timeframe desired. For the case of air
spray
atomisation, air velocities would be adjusted. The presence of pressurized air
means
a greater degree of control could be exerted over the spray. By varying air
pressure,
the shape and level of atomisation can be changed without affecting fluid
pressure.
[0061] Finally, a system for air atomisation using air could be based on the
Venturi effect.
The Venturi effect is also based on the Bernoulli principle. In a Venturi
design, when a
fast gas stream is injected into the atmosphere and across the top of the
vertical tube,
it is forced to follow a curved path up, over and downward on the other side
of the tube.
This curved path creates a lower pressure on the inside of the curve at the
top of the
tube. This curve-caused lower pressure near the tube and the atmospheric
pressure
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further up is the net force causing the curved, velocity-changed path (radial
acceleration) shown by Bernoulli's principle.
[0062] The difference between the reduced pressure inside the Venturi atomiser
and
the higher atmospheric pressure inside the feed reservoir pushes the liquid
from the
reservoir up the tube and into the moving stream of air where it is broken up
into small
droplets and carried away with the stream of air.
[0063] Two-fluid pneumatic atomisation employs the interaction of the slurry
with
another fluid, usually compressed air using a fluid nozzle for the compressed
air and
a fluid nozzle for the slurry. The pressure of the air and slurry may be in
the range of
about 200 to 2000 kPa. Particle size is controlled by varying a ratio of the
compressed
air flow to that of the slurry flow.
[0064] Sonic atomisation employs ultrasonic energy to vibrate a surface at
ultrasonic
frequencies. The slurry is brought into contact with the vibrating surface in
order to
produce the particles/droplets.
[0065] This system may comprise a cyclone for receiving the air/liquid/solids
or
gas/liquid/solid atomised in dispersed droplets and particles. The cyclone may
have:
= the atomiser inlet for introducing the gas/liquid/solid dispersed fluid
into the
cyclone
= an outlet for removing a separated gas/liquid mixture from the cyclone;
= a discharge for removing separated solids from the cyclone;
= a gas/liquid separator connected to the outlet for receiving the
separated
gas/liquid mist from the cyclone and for separating the gas/liquid to a gas
component and a liquid component; and a vacuum system connected to the
gas/liquid separator for providing a motive force for moving the
gas/liquid/solid
mixture into the cyclone, for moving the separated gas/liquid mist into the
gas/liquid separator and removing the gas component from the gas/liquid
separator.
[0066] A cyclone may be used to effect cyclonic separation. Cyclones are
basically
centrifugal separators. They transform the inertia force of gas particle to a
centrifugal
force by means of a vortex generated in the cyclone body. The particle laden
gas
enters tangentially at the upper part and passes through the body describing
the
vortex. Particles are driven to the walls by centrifugal forces, losing its
momentum and
falling to the cyclone. In the lower section, the gas begins to flow radially
inwards to
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the axis and spins upwards to the gas outlet duct. Denser particles in the
rotating
stream have too much inertia to follow the tight curve of the stream, and thus
strike the
outside wall, then fall to the bottom of the cyclone where they can be
removed.
[0067] In the current application, initial inlet velocities are very similar
for solid and
liquid particles. Momentum and centrifugal forces are higher for denser
particles. Some
of the solid particles will impact the cyclone walls while still subject to
centrifugal forces,
moving downwards following the conical shape of the cyclone, these particles
not
subject to Stokes' drag forces, while the remaining solids particles fall
towards the
bottom outlet by gravity and subject to Stokes' drag forces. The very fine
water/liquid
particles will be subject to less momentum and directed towards the top outlet
of the
cyclone with the gas/air flow stream. The gas flow rate is adjusted to provide
the
optimum balance to drive solid particles to the bottom by centrifugal motion
while very
fine water droplets with the gas stream to the top.
[0068] The centrifugal force, F, in a cyclone is given by:
F ¨ pp.ap3.vp2
where:
pp = particle density, (kg/m3)
dp = particle diameter, (pm)
vp = particle tangential velocity, (m/s)
r = radius of the circular path, (m)
[0069] The term "tailings" includes tailings derived from oil sands extraction
operations
and containing a fines fraction. The term includes fluid fine tailings (FFT)
and/or mature
fine tailings (MFT) from tailings ponds and fine tailings from ongoing
extraction
operations (for example, thickener underflow or froth treatment tailings)
which may
bypass a tailings pond.
[0070] Atomisation may be performed using:
= a nozzle technique (e.g. an atomising nozzle),
= an air spray/atomisation technique
= a venturi principle-based technique
= a centrifugal technique (directing a flow onto a rotating disc or wheel),
a
pneumatic technique (e.g. directing a flow into an air stream), and
= an ultrasonic technique (using a vibrating surface to produce droplets).
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[0071] The classifier may have a cyclone with a vacuum system to provide the
motive
force for moving the gas/liquid/solid mixture into the cyclone.
[0072] This technology may be applied in:
= Separation of mineral slurries in mining and mineral-processing
industries
= Dewatering of fluid, fine tailings and mature fine tailings in the oil
sands
= Dewatering and solids control of drillings fluids in the oil & gas
industry
= Separation of solids from gas-solid streams in industrial operations,
including
oil & gas production operations
= Separation of liquids and solids from gas streams in oil & gas production

operations
= Separation of solids from water for water disposal in oil & gas midstream

operations
= Dewatering of industrial sewage
= Dewatering of fine coal (tailings from coal plants)
= Removal of particulates from a liquid stream in natural products
= Removal of water in food industry applications
= Removal of water in pharmaceutical and biotechnology applications
BRIEF DESCRIPTION OF THE DRAWINGS
[0073] Various objects, features and advantages of the invention will be
apparent from
the following description of particular embodiments of the invention, as
illustrated in
the accompanying drawings. The drawings are not necessarily to scale, emphasis

instead being placed upon illustrating the principles of various embodiments
of the
invention. Similar reference numerals indicate similar components.
Figure 1 is a schematic diagram of an embodiment of a dewatering system for
dewatering tailings.
Figure 2 is a schematic diagram of an embodiment of an apparatus for
reducing the particulate content of a liquid-particulate mixture.
Figure 3 is a schematic diagram of a further embodiment of an apparatus for
reducing the particulate content of a liquid-particulate mixture.
Figure 4 is a schematic diagram of a further embodiment of an apparatus for
reducing the particulate content of a liquid-particulate mixture.
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Figure 5 is a schematic diagram of a further embodiment of an apparatus for
reducing the particulate content of a liquid-particulate mixture.
Figure 6a is a side cross-sectional view of an air atomising device showing a
solid-liquid mixture being atomised.
Figure 6b is a front view of the air atomising device of figure 6a.
Figure 7 is a particle distribution of droplet size diameter produced by an
atomiser.
DETAILED DESCRIPTION
Introduction
[0074] Given the significant inventory of mature tailing and ongoing
production of fine
tailings at oil sands operations, there is a need for techniques and advances
that can
enable fine tailings and mature fine tailings dewatering and drying for
conversion into
reclaimable landscapes.
[0075] Preferably, the solution should have low operating costs, low capital
costs, high
processing flow rates, and/or a reduced or no need of chemical additives. This
helps
enable reclamation of tailings disposal areas and recovery of water for
recycling.
[0076] The present technology involves dewatering oil sands tailings via an
atomisation/atomising process that disperses the tailings fluids into water,
solids and
oil droplets (at micro scale) in a gaseous (e.g. air) medium and separates
them from
each other. The liquid (water) droplets are dispersed at the same scale of the
existing
solid fines particles (discretizing the system at the same relative scale).
This can help
allow the system distinguish between particles of different densities rather
than
between particles of different sizes, because the size of the particles are
similar.
[0077] In particular, the present technology relates to an apparatus and
method for
reducing the particulate content of a liquid-particulate mixture or a gas-
liquid-
particulate mixture. The apparatus has an atomiser and a gas-flow classifier.
The
atomiser receives the liquid-particulate mixture and atomises it into a very
fine mist,
wet fog or spray. The gas-flow classifier receives the atomised liquid-
particulate
mixture from the atomiser and directs the atomised particle towards one of two

classifier outlets based on the liquid-solids ratio of the particles.
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Dewatering System
[0078] Figure 1 is a flow diagram of a system according to the present
disclosure.
[0079] The system comprises a dewatering apparatus reducing the particulate
content
of a liquid-particulate mixture, the apparatus comprising:
an atomiser 102, the atomiser configured to receive the liquid-particulate
mixture and to atomise the liquid-particulate mixture; and
a gas-flow classifier 103 configured:
to receive the atomised liquid-particulate 106 mixture from the atomiser 102;
and
to direct individual atomised particles through a gas chamber 107 towards one
of two classifier outlets 104, 105 based on the liquid-solids ratio of the
particles.
[0080] In this case, the liquid-particulate mixture is obtained from a
tailings pond 131.
The tailings are primarily Mature Fine Tailings (MFT, also known as fluid fine
tailings,
FFT). It will be appreciated that the present technology may be used to reduce
the
particulate content of any liquid-particulate mixture such as from tailings
ponds or
tailings from ongoing oil sands extraction operations.
[0081] In this case, the tailings are from a bitumen extraction process.
Within the
tailings pond, the tailings stream settles and separates into an upper water
layer, a
middle MFT/FFT layer, and a bottom layer of settled solids. The MFT/FFT layer
is
removed for processing by the dewatering apparatus from between the water
layer
and solids layer via a dredge 132 (e.g. a floating barge having a submersible
pump).
[0082] In this case, the MFT/FFT feed 111 has a solids content ranging from
about 10
wt. % to about 45 wt.% (in other embodiments, the MFT/FFT may have a solids
content
ranging from about 30 wt.% to about 40 wt. %). In this case, the MFT/FFT is
undiluted.
[0083] Before being transferred to the dewatering apparatus, the MFT/FFT 111
is
passed through a screen 133 to remove any oversized materials. The screen may
form
part of a shale shaker. The screen size is designed to avoid slow filtration
rates, but to
provide a filtration performance enough to guarantee unobstructed flow, so a
screen
mesh with sizes between 0.4 mm to 4 mm (e.g. mesh #40 to #5) may be used. The
resulting liquid-particulate mixture 112 has fewer large particulates. By
filtering out
oversized materials, clogging during the process and of the atomiser or
atomisation
system 102 may be mitigated.
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[0084] In this case, the screened MFT/FFT is collected in a feed vessel 134
such as
a tank. Using a feed vessel allows the flow rate of the feed to the dewatering
apparatus
to be regulated.
[0085] In this embodiment, the MFT/FFT is then pumped via a pump 135 from the
feed
vessel 134 through the atomiser 102. The atomiser 102 in this case comprises
an
atomising nozzle. The atomising nozzle is configured to generate an atomised
liquid-
particulate spray of particles. The table below illustrates some of
denominations used
in industrial spray for droplet sizes produces after atomisation.
[0086] Table 1: Spray droplet size classifications
Spray droplet size classifications
Droplet diameter (urn) Type of droplet
(Very fine) Dry fog
(Very fine) Dry fog
(Very fine) Wet fog
50 (Very fine) Wet fog
100 (Very fine) Fine mist
200 (Fine) Fine drizzle
300 (Medium) Fine rain
500 (Very coarse) Light rain
[0087] According to the classification, the system is expected to produce very
fine
particles/droplets (e.g. less than 100 microns). At least 50% of the particles
produced
by the atomiser may have diameter of between 0.5-20 microns. 50% of the
particles
might have a diameter between 20 to 70 microns. For purpose of this
application, a
target Dv50 = 20 pm. At least 90% of the particles should have a diameter
below 40
pm, this is Dv90 = 40 urn. Figure 7 shows an example of a target particle size

distribution.
[0088] It will be appreciated that some of the particles may be pure liquid
droplets;
some particles may be solid particles; and some particles may be a mixture of
solid
and liquid phases.
[0089] The atomiser 102 is configured to spray 106 the atomised liquid-
particulate
mixture into a gas-flow classifier. As noted above, the classifier comprises a
gas
chamber 107 and two outlets 104, 105.
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[0090] In this case, the gas chamber is configured to contain air as the drag
medium.
As the atomised liquid-particulate spray of particles pass through the gas
they
experience a drag. Therefore, each particle will have an initial velocity and
will be acted
upon by various forces including, in this case, the force of gravity and the
drag force
applied by the gas. This causes the various particles to move along different
trajectories based on their liquid-solids ratio (e.g. based on their density).
[0091] It will be appreciated that the outlet configuration (position, size)
and the
atomising nozzle configuration (velocity, orientation) may be adjusted in
order to
control the separation of the liquid and solid particles. For example, if
purer water was
desired, the dewatering apparatus may be configured such that the reduced-
solids
outlet 104 only receives particles close to the density of water (1g/cm3).
However, this
may lead to particles with a significant water content being directed to the
reduced-
liquid outlet 105. In this case, the apparatus is configured to produce, from
a feed
containing 30% solids and 70% water by weight, a reduced-solids output 113
containing 10% solids and 90% water by weight; and a reduced-liquid output 114

containing 70% solids and 30% water by weight.
[0092] The reduced-liquid output 114 can be applied to reclamation land 137.
[0093] The reduced-solids output can be processed further in a reduced-solids
processor 136 to further separate solids from the liquid. The liquid output
115 from the
reduced-solids processor may be recycled as water, and the solids output 116
may be
applied to reclamation land 137. The reduced-solids processor may comprise a
further
dewatering apparatus comprising an atomiser and a gas-flow classifier.
[0094] Lower density particles correspond with particles with higher water
content as
water is less dense than the mineral solids which typically make up fines in
tailing
ponds. Higher density particles correspond with particles with higher solid
content.
[0095] In this embodiment, the classifier is configured such that higher
liquid-solids
ratio droplets are directed towards the upper outlet 104 (which is located
opposite the
atomiser on the side of the gas chamber 107). In contrast, lower liquid-solids
ratio
particles are directed towards the lower outlet 105 (which is located at the
bottom of
the gas chamber 107).
[0096] It will be appreciated that, in other embodiments, the classifier may
be
configured so that most of solids go to the top while most of the water is
streamed to
the bottom.
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Separating Apparatus Embodiment
[0097] Another embodiment of a dewatering or separating apparatus is shown in
figure
2.
[0098] Figure 2 shows a system for spraying and dewatering a liquid-solids or
suspension effluent into a lower solids content fluid without applying heat,
comprising:
pumping the liquid effluent as a slurry or suspension; passing the suspension
or slurry
through and atomising device, atomising the charged slurry to produce fine
droplets of
water (and oil) and dispersed solid particles, co-flowing with a stream of air
inside a
cyclone.
[0099] Like the previous system, this apparatus comprises:
an atomiser 202, the atomiser configured to receive the liquid-particulate
mixture and to atomise the liquid-particulate mixture; and
a gas-flow classifier 203 configured:
to receive the atomised liquid-particulate mixture 206 from the atomiser 202;
and
to direct individual atomised particles through a gas chamber 207 towards one
of two classifier outlets 204, 205 based on the liquid-solids ratio of the
particles.
[0100] In this case, the atomiser 202 is feed from a feed vessel or reservoir
241 (e.g.
a 150-200 litre tank). Gas is pumped by a compressor 245 through a Venturi
section
246 (e.g. a constricted or choke section within a pipe which increases the
velocity and
lowers the pressure of the fluid passing through this section). When gate
valve 247 is
open this draws the liquid-particulate mixture from the feed vessel 241 and
directs the
liquid-particulate mixture through the atomiser 202. As before, the liquid-
particulate
mixture may have a solids content of 20-40% by mass.
[0101] Unlike the previous embodiment, the two outlets 204, 205 of the gas-
flow
classifier 203 in this embodiment are arranged on the top and the bottom of
the gas
chamber 207. In this case, gas is drawn up through the gas chamber by a pump
244.
This means that there is a gas flow relative to the gas chamber within the gas
chamber.
The gas inlets and outlets are configured to induce helical gas flow up though
the gas
chamber to form a cyclone.
[0102] When the liquid-particulate mixture 206 from the atomiser 202 impinges
on the
gas flow through the gas chamber 203, the higher liquid-solids ratio particles
are
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directed upwards towards the solids-reduced outlet 204, whereas the lower
liquid-
solids ratio particles are directed downwards towards the liquid-reduced
outlet 205. In
this way particles with higher liquid content are separated from particles
with higher
solid content.
[0103] Conduit 215 is configured to transfer the solid-reduced output and gas
to a
solid-reduced vessel 243. Conduit 214 is configured to transfer the liquid-
reduced
output to a liquid-reduced vessel 242.
Further Separating Apparatus
[0104] Figure 3 shows a further embodiment for spraying and dewatering a
liquid-
solids or suspension effluent into a lower solids content fluid without
applying heat.
[0105] Like the previous system, this apparatus comprises:
an atomiser 302, the atomiser configured to receive the liquid-particulate
mixture and to atomise the liquid-particulate mixture; and
a gas-flow classifier 303 configured:
to receive the atomised liquid-particulate mixture 306 from the atomiser 302;
and
to direct individual atomised particles through a gas chamber 307 towards one
of two classifier outlets 304, 305 based on the liquid-solids ratio of the
particles.
[0106] In this case, the atomiser 302 is feed from a feed vessel 341 (e.g. a
150-200
litre tank). In this embodiment, the liquid-particulate mixture is pumped
using a
progressive cavity pump 349 to the atomiser. A gate valve is positioned
between the
pump 349 and the feed vessel 341 which can be used to isolate the pump 349
from
the feed vessel 341. As before, the liquid-particulate mixture may have a
solids content
of 20-40% by mass.
[0107] Like the previous embodiment, the two outlets 304, 305 of the gas-flow
classifier 303 in this embodiment are arranged on the top and the bottom of
the gas
chamber 307. Gas is drawn up through the gas chamber by a pump 344. This means

that there is a gas flow relative to the gas chamber within the gas chamber.
When the
liquid-particulate mixture 306 from the atomiser 302 impinges on the gas flow
through
the gas chamber 303, the lower density particles are directed upwards towards
the
solids-reduced outlet 304, whereas the higher density particles are directed
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downwards towards the liquid-reduced outlet 305. In this way particles with
higher
liquid content are separated from particles with higher solid content.
[0108] Conduit 315 is configured to transfer the solid-reduced output and gas
to a
solid-reduced vessel 343. Conduit 314 is configured to transfer the liquid-
reduced
output to a liquid-reduced vessel 342.
[0109] A progressing cavity (PC) pump employs a positive displacement
principle. A
typical PC features a suction inlet which feeds into an elongated casing.
Within this
casing sits a helical 'worm rotor and stator assembly. The rotor helix is
shaped off-set
to the stator creating cavity spaces in the assembly which are formed by
temporary
seals as the rotor contacts the surface of the stator. As the rotor begins to
move in an
eccentric fashion, the cavities form, draw in product and are 'progressed'
along the
assembly and the product is expelled through the discharge port. This leads to

the volumetric flow rate being proportional to the rotation rate
(bidirectionally) and to
low levels of shearing being applied to the pumped fluid.
[0110] Typical fluids pumped by PC pumps include slurry, mashes, pulps, dough
from
waste water treatment plants, anaerobic digestion facilities and paper
recycling plants.
PC pumps can be adapted and specified with a range of accessory components and

configurations to accommodate the difficult fluids are expected to handle,
such as:
adjusting the feed inlet with different screw and paddle feeders to break up
big solids,
mechanical seal arrangements to protect against highly abrasive wear.
It is appreciated that there are different pump technologies that can handle
solids and
that could be used within these applications. Such pumps include centrifugal
pumps
and other types of positive displacement pumps such as diaphragm pumps.
Venturi Embodiment
[0111] Figure 4 shows a further embodiment for spraying and dewatering a
liquid-
solids or suspension effluent into a lower solids content fluid without
applying heat.
[0112] Like the previous system, this apparatus comprises:
an atomiser 402, the atomiser configured to receive the liquid-particulate
mixture and to atomise the liquid-particulate mixture; and
a gas-flow classifier 403 configured:
to receive the atomised liquid-particulate mixture 406 from the atomiser 402;
and
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to direct individual atomised particles through a gas chamber 407 towards one
of two classifier outlets 404, 405 based on the liquid-solids ratio of the
particles.
[0113] In this case, the atomiser 402 comprises a Venturi section 446 and is
feed from
a feed vessel 241 (e.g. a 150-200 litre tank). Gas is pumped by a compressor
445
through the Venturi section 446 (e.g. a constricted or choke section within a
pipe which
increases the velocity and lowers the pressure of the fluid passing through
this
section). When gate valve 447 is open this draws the liquid-particulate
mixture from
the feed vessel 441 and directs the liquid-particulate mixture through the
atomiser 402.
That is, the atomiser in this case draws the feed mixture into itself and
atomizes it. This
may be more energy efficient than using a separate Venturi section and
atomiser. As
before, the liquid-particulate mixture may have a solids content of 20-40% by
mass.
[0114] When the liquid-particulate mixture 406 from the atomiser 402 impinges
on the
gas flow through the gas chamber 403, the higher liquid-solids ratio particles
are
directed upwards towards the solids-reduced outlet 404, whereas the lower
liquid-
solids ratio particles are directed downwards towards the liquid-reduced
outlet 405. In
this way particles with higher liquid content are separated from particles
with higher
solid content.
[0115] The two outlets 404, 405 of the gas-flow classifier 403 in this
embodiment are
arranged on the top and the bottom of the gas chamber 407. In this case, gas
is drawn
up through the gas chamber by a pump 444. Conduit 415 is configured to
transfer the
solid-reduced output and gas to a solid-reduced vessel 443. In this case, the
vacuum
pump is positioned after the solid-reduced vessel 443.
[0116] Conduit 414 is configured to transfer the liquid-reduced output to a
liquid-
reduced vessel 442.
[0117] It will be also appreciated that the outlet configuration (position,
size) and the
atomisation configuration can be used to avoid plugging of the system and/or
to
produce atomisation via the co-flow of air and the fluid within the cyclone.
In this
configuration, fluids are sucked by a Venturi configuration, meeting air only
at the
outlet. This way the process is controlled via the air flow rates. For
instance, higher
flow rates will produce smaller droplet/particles sizes, while a balance needs
to be
reached to reduce the impact of water droplets with the farther wall of the
cyclone.
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Alternative Fan Position
[0118] Figure 5 shows an alternative configuration. In this case, the vacuum
pump is after
the receiving tank 543, and there is a filter 591 to retain small fines that
have made through
the top, the liquid at this stage are coalesced drop and expected to settle at
the bottom of
tank/separator 543. Water can be removed from this receiving tank 543, which
in this case is
in the form of a drum.
[0119] Like the previous system, this apparatus comprises:
an atomiser 502, the atomiser configured to receive the liquid-particulate
mixture and
to atomise the liquid-particulate mixture; and
a gas-flow classifier 503 configured:
to receive the atomised liquid-particulate mixture 506 from the atomiser 502;
and
to direct individual atomised particles through a gas chamber 507 towards one
of two
classifier outlets 504, 505 based on the liquid-solids ratio of the particles.
[0120] In this case, the atomiser 502 is feed from a feed vessel 541 (e.g. a
150-200 litre
tank). Gas is pumped by a compressor 545 through a Venturi section 546 (e.g. a
constricted
or choke section within a pipe which increases the velocity and lowers the
pressure of the
fluid passing through this section). When gate valve 547 is open this draws
the liquid-
particulate mixture from the feed vessel 241 and directs the liquid-
particulate mixture through
the atomiser 502. As before, the liquid-particulate mixture may have a solids
content of 20-
40% by mass.
[0121] When the liquid-particulate mixture from the atomiser 502 impinges on
the gas flow
through the gas chamber 503, the higher liquid-solids ratio particles are
directed upwards
towards the solids-reduced outlet 504, whereas the lower liquid-solids ratio
particles are
directed downwards towards the liquid-reduced outlet 505. In this way
particles with higher
liquid content are separated from particles with higher solid content.
[0122] The two outlets 504, 505 of the gas-flow classifier 503 in this
embodiment are
arranged on the top and the bottom of the gas chamber 507. In this case, gas
is drawn up
through the gas chamber by a pump 544, which in this case is an induced draft
fan. A conduit
is configured to transfer the solid-reduced output and gas to a solid-reduced
vessel 543. In
this case, the vacuum pump is positioned after the solid-reduced vessel 543.
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[0123] A conduit is configured to transfer the liquid-reduced output to a
liquid-reduced
vessel 542.
[0124] It will be also appreciated that the outlet configuration (position,
size) and the
atomisation configuration can be used to avoid plugging of the system and/or
to
produce atomisation via the co-flow of air and the fluid within the cyclone.
In this
configuration, fluids are sucked by a Venturi configuration, meeting air only
at the
outlet. This way the process is controlled via the air flow rates. For
instance, higher
flow rates will produce smaller droplet/particles sizes, while a balance needs
to be
reached to reduce the impact of water droplets with the farther wall of the
cyclone.
Atomisation
[0125] Figures 6a-b shows an air atomising nozzle 602 having a centrally
located
liquid 612 outlet and two active gas 695 outlets. It will be appreciated that
other gas
atomising nozzles may have different configurations of outlets (e.g. more than
two gas
outlets).
[0126] In this embodiment, the compressed air 695 does not enter in contact
with the
fluid 612 until they both go through the outlet. In this case the fluid 612
does not go
through a narrow constriction, and droplets 606 are produced due to the energy
input
of high velocity air 695.
Experimental Results
[0127] A basic proof of concept was conducted at small scale. Fluids were
atomised
with a batch of 2 litres of mature fine tailings. Experiments were conducted
at 25 C,
with the fluids at 25 C. The fluid was put into an atomiser bottle. Then the
fluid was
atomised. Dispersion of the fluids in the air was observed. One issue observed
was
the occasional clogging of the nozzle, but during continuous operation the
fluids were
atomised/dispersed in the air. After this, output fluids were collected via
top and bottom
of a collection funnel.
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[0128] Table 1.
Process MFT Solids Solids Content (% Solids Content
Content (% Weight) Output (% Weight)
Weight) Underflow Overflow Output
Atomising/classification ¨40% ¨70% ¨20%
[0129] The fluid prior to atomisation has a solids content ¨40%. The bottom
fluids were
measured to have a solid content around 65-70% as displayed in Table 1. The
fluids
in the top a solids content ¨20% and ¨80% water.
Theory
[0130] The present technology relates to dewatering tailings comprising water
and
fines. Fines are solid mineral particles with a diameter less than 44 microns
(although
this method may work with particle sizes up to 100 microns or larger). It has
been found
that separating suspended particles less than about 44 microns is extremely
difficult.
[0131] The invention involves atomising the tailings into a fine mist then
using the
density, p, and flow patterns of the different components (e.g. within a
cyclone
classifier) to separate solid particles from aqueous components. The density
ranges
are as follows:
= Pure water droplets: p = 1 g/cm3
= Water droplets/solid particles: 1.4 g/cm35 p 5 1.8 g/cm3
= Solid particles: 2.5 g/cm3 p 5 2.9 g/cm3
[0132] Generally, as a result of the different sized particles and their
densities, the
atomiser can provide effective/improved separation of the fine particles from
water.
[0133] Advantages of the proposed method may include that the tailings do not
need
treatment with coagulants, flocculants and/or heat.
[0134] D50 is the value of the particle diameter at 50% in the cumulative
distribution.
D50 can use volume, mass or number as reference. Here, the volume reference is

used, Dv50. Dv50 is also known as the volume median or volume average particle

size, it physically represents that each volume of particles greater or
smaller than such
value takes account of 50% of the total particles volume. Similarly, the
volumetric 90%
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CA 03127837 2021-07-26
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PCT/CA2020/050130
particle size, Dv90, is the value of the particle diameter at 90% of the
cumulative
volume distribution.
[0135] As noted above, previous devices to separate liquids (and liquids and
solids)
have relied on heating the mixture until at least one of the liquid phases is
converted
into a gas. In contrast, in the current technology, the liquid phase does not
need to go
through a phase change to be separated from the other (i.e. solid) phases. Not
using
vaporization is important, because evaporation is an energy intensive process.
The
increase in surface area achieved with the atomisation increases the rate of
heat
transfer, but that does not change the heat of evaporation required. The
energy
consumption of industrial spray driers is in average 4.87 GJ/t.
[0136] The separation based on density is due to the particles' interaction
with a gas
medium (e.g. including drag effects). For example, it is known that in the
absence of
drag, objects with the same initial velocity will follow the same trajectory
regardless of
mass or density. For example, the trajectory will be the same for dropping
water and a
solid object.
[0137] Drag is generated by the difference in velocity between the solid
object and the
gas/fluid (in this case air). There must be motion between the object (e.g.
solid) and
the fluid (e.g. air). If there is no motion, there is no drag. It makes no
difference whether
the object moves through a static fluid or whether the fluid moves past a
static solid
object. Drag is a force and is therefore a vector quantity having both a
magnitude and
a direction. Drag acts in a direction that is opposite to the motion of the
solids.
[0138] The drag force depends on the shape of the object. Therefore, two
objects of
the same size travelling at the same speed through a fluid will experience the
same
drag force. However, if one of the objects has less mass (or is of a lower
density), this
same drag force may cause a larger deceleration.
[0139] In addition, the drag on solid particles may be different than the drag
on liquid
particles, because the small solid particles are not compressible or
elongated, while
liquid particles elongate and thus are exposed to less overall drag.
[0140] Also, for terminal velocities, Stokes' law applies. The force of
viscosity on a
small sphere moving through a viscous fluid is given by:
Fd = 67r Rv
where:
- 25 -

CA 03127837 2021-07-26
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PCT/CA2020/050130
= Fd is the frictional force ¨ known as Stokes drag ¨ acting on the
interface
between the fluid and the particle;
= is the dynamic viscosity;
= R is the radius of the spherical object;
= v is the flow velocity relative to the object.
[0141] If the particle is falling in the viscous fluid under its own weight,
then a terminal
velocity, or settling velocity, is reached when this frictional force combined
with the
buoyant force exactly balances the gravitational force. This velocity v (m/s)
is given by:
2 (pp Pf)g R2
v =
9 1-1
where:
= g is the gravitational acceleration (m/s2)
= R is the radius of the spherical particle.
= pp is the mass density of the particles (kg/m3)
= pf is the mass density of the fluid (kg/m3)
= p is the dynamic viscosity (kg/m*s).
[0142] For particle densities higher than the fluid (in this case air)
densities, the particle
still tends to fall. The main difference is that due to density difference,
solid particles
with densities of i.e. 2.6 g/cm3 will fall considerably faster than particle
with densities
of 1 g/cm3.
[0143] In summary, in the first step fluid is atomised from the outlet of an
atomiser
(which could come from a venturi) with the outlet slightly inclined upwards,
so that all
particle will be exposed to different types of drags. First, as particles are
expelled at a
relatively high velocity, solid particles may experience higher drag than
liquid particles
due to shape effects, as liquid particles are deformable and may be elongated
in the
direction of the flow. Solid particles experiencing higher drag lose their
initial velocities
faster, falling first. Eventually, some liquid particles tend to fall. But
even at this stage,
both types of particles are subject to Stokes' drag, and solid particles fall
faster due to
density difference.
[0144] For a water particle 25 um, assuming no air flow, the Stokes law
falling velocity:
(vf) corresponds to 0.018 m/s. In contrast, for a solid clay 25 um, assuming
no air flow,
the Stokes terminal velocity (vf) is 0.048 m/s.
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CA 03127837 2021-07-26
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[0145] In some embodiments, a surfactant could be added to MFTs to reduce the
surface tension of the system and obtain smaller water droplet size.
[0146] Although the present invention has been described and illustrated with
respect
to preferred embodiments and preferred uses thereof, it is not to be so
limited since
modifications and changes can be made therein which are within the full,
intended
scope of the invention as understood by those skilled in the art.
Bibliography
[0147] Chalaturnyk R.J. et al., 'Management of Oil Sands Tailings, Petroleum
Science
and Technology", 20:9-10, 1025-1046 (2002)
[0148] Jeeravipoolvarn S. 'Compression behaviour of Thixotropic Oil Sands
Tailings",
M.Sc. Thesis, University of Alberta (2005)
[0149] Roshani A., "Drying Behavior of Oil Sand Mature Fine Tailings Pre-
dewatered
with Superabsorbent Polymer", Ph.D. Thesis, University of Ottawa (2017)
[0150] Tang J., 'Fundamental Behaviour of Composite Tailings", M.Sc. Thesis,
University of Alberta (1997)
- 27 -

Representative Drawing
A single figure which represents the drawing illustrating the invention.
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Administrative Status

Title Date
Forecasted Issue Date 2022-03-08
(86) PCT Filing Date 2020-02-04
(87) PCT Publication Date 2020-08-13
(85) National Entry 2021-07-26
Examination Requested 2021-08-23
(45) Issued 2022-03-08

Abandonment History

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Owners on Record

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Current Owners on Record
ENOVIST INC.
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None
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