CA3127837A1 - Systems and methods for reducing the particulate content of a liquid-particulate mixture - Google Patents

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.

Description

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 (CHVVE). 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 CHVVE process achieves over 90% bitumen recovery efficiency at about 85 C and pH of 8.5.

[0004] In the commercial oil sands operations using CHVVE, 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 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.

[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 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 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.

[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 35 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 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.

[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.

48 [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 (P1 \ 0:

[0051] Where D1 is the mean droplet size at pressure 'I (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.

[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 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 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*dP3*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).

[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.

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.

Dewate ri ng 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.

[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 um. 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.

[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.

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 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 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 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 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 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.

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.

[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 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. 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.

[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.

[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/cm3 p 1.8 g/cm3 = Solid particles: 2.5 g/cm3 p 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%

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 = 67riffiv where:

= Fd is the frictional force ¨ known as Stokes drag ¨ acting on the interface between the fluid and the particle;
= pt 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 (p¨ p) gR2 = ______________________________________ 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 airflow, the Stokes law falling velocity:
(vt) corresponds to 0.018 m/s. In contrast, for a solid clay 25 um, assuming no air flow, the Stokes terminal velocity (vt) is 0.048 m/s.

[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)

Claims (21)

PCT/CA2020/050130

1. 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.

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, each particle having a particular liquid-solids ratio.

3. The apparatus according to any one of claims 1-2, wherein the atomiser is configured to receive a pre-existing gas stream containing a liquid-particulate mixture, and to further disperse the liquids-particulates into smaller particles, each particle having a particular liquid-solids ratio.

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.

9. The apparatus according to any one of claims 1-8, wherein the apparatus comprises a gas pump 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 liquid to solid ratios of the reduced-solids reduced-liquid outputs.

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, 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 of the particles.

21. The method of claim 20, wherein the liquid-particulate mixture is extracted from a tailings pond.