This invention relates to a method and apparatus for the volume reduction of fine particulate and more particularly to the volume reduction of mine tailings by promoting the dense packing of the discrete solid particles or by infusing tailings sludge into the spaces between those solid particles.
Human consumption of minerals and fossil fuels continues at an ever-increasing rate. Both the mining industry and the oil and gas industry produce large quantities of tailings that require disposal. These tailings must be disposed of in an environmentally safe and cost effective manner.
Tailings are produced as a by-product in both the mining and oil and gas industry. For example, hard rock mining extracts minerals from ore by first pulverizing the rock into fine particles, from which the minerals are extracted using chemicals. The processed fine particles or “tailings” are typically small, ranging in size from the size of a grain of sand down to a few micrometres.
In oil sands mining, loose sand and partially consolidated sandstone that are saturated with bitumen are treated to separate and recover the valuable bitumen, with the remaining treated material placed in a tailing pond. In addition to the particulate matter, large quantities of water wind up in the tailings ponds which take decades to settle.
Efforts are being made to accelerate the settling of tailings ponds. For example, one strategy involves dredging mature tailings from the bottom of the tailings pond, mixing the mature tailings with a polymer flocculent and then spreading the resulting mixture over a “beach” with a shallow grade. This is claimed to reduce the time to reclaim a tailing pond from 40 years to 7-10 years.
There is neither a practical method nor an apparatus available to the mining and oil/gas industries to either minimize the volume of solid particles after they enter the tailing pond or to maximize recovery of the fluid within the tailing pond for reuse. In the absence of any practical way to deal with the large amounts of semi-fluid waste products discharged from the mine milling process, several mines have had to shut down production for the want of storage volume in environmentally acceptable terrain and within economical proximity to the ore body and milling facilities.
Accordingly, it is an object of the present invention to provide methods and apparatus for either promoting the dense packing of the discrete solid particles, or accommodating very fine viscous sludge within the void spaces between coarser particles.
It is a further object of an embodiment of the invention to provide a method and apparatus for reducing a tailing pond and enabling the recovery of the liquid contained therein.
The present invention relates to a method and apparatus for the volume reduction of fine particulate and more particularly to the volume reduction of mine tailings by promoting the dense packing of the discrete solid particles using a poker equipped with a paddle for mixing together strata of various sized particles and imparting vibration.
In another embodiment, the invention comprises a mixing assembly comprising a poker that can be raised or lowered into material to be mixed, the poker having an outer casing housing a spiral coupling connected to at least one paddle, said paddle having a radially restrained position and a radially extended position, and the spiral coupling adapted to rotate the paddle and/or transmit vibrations to the paddle.
In another embodiment the invention relates to a method and apparatus for infusing sludge from mine tailings into the pre-existing void between larger particles using a poker equipped with a paddle for mixing the particles and imparting vibration.
In yet another embodiment, the apparatus facilitates the introduction of pressurized fluid, such as cement grout or tailings slimes, into the material being mixed by the paddles at the base of the poker.
According to an embodiment of the invention, the apparatus for the compaction of fine particulate comprises a poker for insertion into the particulate, the poker comprising an elongated cylindrical outer casing mountable to a delivery vehicle, with a drive shaft extending within the outer casing and operatively connected to a rotatable coupling. At least one elongate element is connected at one end to the rotatable coupling and at an opposite end to a nose cone, and is movable from a first position to a second position radially extended from the outer casing.
In another aspect, the elongate element comprises a paddle. The paddle has a top portion, an intermediate portion and a bottom portion; wherein the top portion being hingedly connected at a first end to the rotatable coupling and at a second end to the intermediate portion, and the bottom portion being hingedly connected at a top end to the intermediate portion and at a bottom end to the nose cone. The nose cone is adapted for penetrating the particulate. The paddle is rotatable relative to the outer casing. The rotatable coupling is adapted to transmit rotation or vibration.
In another aspect, the rotatable coupling comprises an upper spiral coupling connected to the drive shaft and a lower spiral coupling rotatably connected to a lower end of the outer casing. A weight is seated on the upper spiral coupling and the lower spiral coupling is seated within a bushing or roller bearing with seals, which in turn is connected to the lower end of the outer casing.
In another aspect rotation of the upper spiral coupling in a first direction causes the lower spiral coupling to rotate, and rotation of the upper spiral coupling in an opposite direction results in vertical forces being applied to the lower spiral coupling thereby causing vibration.
In another aspect, the invention further comprises a central actuating element extending within the outer casing and connected at a lower end to the nose cone. The central actuating element is actuatable to move the elongate element from the first position to the second position.
In another aspect, the central actuating element comprises a threaded shaft.
In another aspect, the central actuating element comprises a cable actuatable by a cable winch.
In another aspect, the central actuating element comprises a pipe. The nose cone has a hollow upper portion having a cylindrical side wall having holes therein. The pipe is in fluid communication with a source of fluid to be dispensed through the holes of the cylindrical side wall.
In another aspect, the nose cone has at least one fluke.
In another aspect, the outer casing has holes defined therein and a mesh screen connected thereto.
In another embodiment, the invention comprises a method for compacting particulate material by inserting a poker into particulate material to be compacted, the poker having at least one stirring element extendible from a first position for penetrating the particulate material when the poker is inserted to a second position extending radially outward from the poker, extending the stirring element from the first position to the second position; and alternately rotating the stirring element through the particulate material and causing the stirring element to vibrate.
In another embodiment, the invention comprises a method for minimizing the volume occupied by the combined volumes of a volume of particulate material and a separate volume of viscous fluid by inserting a poker into the particulate material and dispersing the viscous fluid through the poker into the particulate material surrounding the poker, thereby filling void space between adjacent particulate with the viscous fluid.
The foregoing was intended as a broad summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims.
a is a side view of the bottom portion of the mixing apparatus shown in
b is a bottom view of the mixing apparatus shown in
a is a side view of the bottom portion of the mixing apparatus shown in
b is a bottom view of the mixing apparatus shown in
a is a side view showing the nose cone and its connection to the paddles of the mixing apparatus.
b is an enlarged sectional view of the upper part of the nose cone showing the fluid discharge holes.
a to 10d show the spiral coupling forming an internal hammer and drive mechanism according to the invention.
a is a partial sectional view of the power box shown in
b is a partial sectional view of the power box shown in
a is a side view of the bottom portion of the mixing apparatus shown in
b is a bottom view of the mixing apparatus shown in
a is a side view of the bottom portion of the mixing apparatus shown in
b is a bottom view of the mixing apparatus shown in
The preferred embodiment of a mixing apparatus 10 is shown on a ground deployment vehicle 2 in
Ground deployment vehicle 2 can take the form of any suitable motorized vehicle as known in the art, capable of mobile operation, maneuvering and deploying the mixing apparatus of the invention. Similarly, the water-based deployment vessel 22 can take the form of any suitable motorized vessel, such as a barge or the like, capable of mobile operation, maneuvering and deploying the mixing apparatus of the invention.
The deployment vehicle 2 and vessel 22 are each equipped with a mast 4 having a slide mount 6 driven by a double acting piston located within the mast 4. A power box 8 is connected to, and suspended from, the mount 6, and houses a rotation motor drive and a cable winch. An elongated, cylindrical poker 12 having actuatable paddles 14 is connected to and suspended from the power box and may be inserted into, and removed from the material to be treated, either the ground 20 (for the ground deployment vehicle 2) or the water 24 and ground/tailings 28 requiring treatment (for the water-based deployment vessel 22).
Preferably, for the water-based deployment vessel 22, the vessel is equipped with a central opening, such as moon-pool 26 through which the poker is inserted into the liquid and the material to be treated. This system alleviates any stability concerns for the vessel, by centering the weight within the vessel.
As best shown in
A cylindrical drive shaft 38 extends from the rotation motor drive in the power box 8 to an upper spiral coupling 44 to which it is fixedly connected by welding or the like. A lower spiral coupling 48 is seated within bushing 50 and is freely rotatable and vertically retained therein. The various components may be made of any suitable material; for example, drive shaft 38 may be made of mild steel pipe or tubing.
Preferably the spiral couplings are made of mild steel with case-hardened opposing faces for withstanding the impact forces when the bottom of the upper spiral coupling 44 and the top of the lower spiral coupling 48 come into contact with one another as discussed in more detail below.
A plurality of deployable paddles or elongate members 14 are hingedly connected at one end to the lower spiral coupling 48 and are hingedly connected at the other end to a hub 55 (shown in
A central actuating element in the form of cylindrical central open pipe 37 extends from the power box 8 to the nose cone 32, within the interior of cylindrical drive shaft 38. As shown in
Preferably, the lower portion of outer casing 30 has a plurality of drainage holes 56 defined therein (by drilling, machining or the like) which are covered by a filter/mesh screen 58 to prevent solids from entering into the interior of the outer casing 30. A common submersible or air-lift pump (not shown for clarity) could be used to withdraw any liquids draining into outer casing 30 through holes 56 and convey it to the surface for further processing or treatment and recycling.
Deployment
The operation of the mixing apparatus will be described in more detail with reference to
After insertion into the material to be treated to a desired depth, mixing paddles 14 are deployed. The mixing paddles are preferably longitudinally extending arms, comprised of three portions, top and bottom longer portions 13 and 15 and a smaller central portion 17, the smaller central portion 17 hingedly 42 connected to the top 13 and bottom 15 portions.
The spiral coupling mechanism is designed to transmit rotation, or alternatively, vibration by way of hammer blows, depending on the direction of axial rotation applied to top section of the paired parts by way of cylindrical drive shaft 38 being driven by a rotational drive motor 74 (shown in
As shown in
Preferably nose cone 32 is equipped with flukes 57, which resist rotational movement when the nose cone 32 is inserted into a material to be treated. In this fashion, the torque applied to the connection point between the nose cone and central open pipe 37 is limited.
The spiral coupling mechanism is a mechanism whereby a pair of surfaces is in intimate vertical contact but with their vertical separation dependent on the relative degree of rotation of its two parts. The principle underlying the functionality of the spiral coupling is that the elevation of any point on the surface of the spiral is directly proportional to both its radial distance from the vertical axis, and also to the angular rotational separation/translation (degrees) from the lowest datum.
When rotated clockwise, upper spiral coupling 44 is free to rotate over lower spiral coupling 48, moving up and down as illustrated in
The upper spiral coupling 44 rotates around its vertical central axis as dictated by the torque from the drive shaft 38 to which it is solidly affixed/welded. The lower spiral coupling 48 is solidly affixed/welded to upper paddle arm(s) 13, transmitting either the vibration or rotation depending on the rotation of upper spiral coupling 44.
As the operator finds advantageous, the rotational direction of the drive shaft may be alternated between rotation of the paddles, or vertical vibrations being introduced into the tailings/soil. The speed at which the drive shaft is made to turn while rotating the paddles might be set in the order of 1 to 10 RPM, whereas in its vibration function it might be set at about 1500 RPM or any suitable rate.
The concurrent use of the vertical vibrations (hammer blows per rotation rate) together with the agitation of the surrounding tailings mass is intended to complement the degree of densification of the solid phase.
While a preferred paddle has been described herein, it is also contemplated that other paddle designs would work, provided the paddles can move from a radially constrained position for penetrating the material to be treated and a radially extending position for treating the material. The paddles may also be shaped as hydrodynamic foils such that their rotation can serve to elevate the whole assembly out of the mass in which it is immersed/deployed.
By continuing to cause the paddles or wings to rotate as the tubular body of the mechanism is gradually withdrawn (by double acting piston slide mount 6) from its initial penetrated depth within the tailings or material mass, the full depth of the material within the compass of the apparatus will be thoroughly mixed. Alternatively, if treatment at a given layer is all that is required, the paddles may be moved back into penetration mode by releasing the pipe clamp 75 from central pipe 37 and then withdrawing the poker 12 using piston slide mount 6.
While a single poker deployment vehicle has been shown and described, it is also contemplated that a single surface transportation vehicle could be used to deploy several, suitably arrayed, mechanisms of this type in order to treat a larger aerial extent than attainable by a single apparatus, and in the same time.
How the Method would Work in Practice
The method will now be described in more detail with reference to treatment of tailings. This method could be applied to any particulate requiring treatment; for example, to geotechnical problems in river deltas.
Instances of the apparatus, either singly or in a multiple array, would be taken to a chosen location by a suitable deployment vehicle (tractor or barge), and made to enter the tailings mass vertically to a desired depth. Penetration of material to be treated can be assisted by the activation of the spiral coupling vibration function at an appropriate rate of rotation. Furthermore, the gradual withdrawal of the mechanism can be assisted by the paddles when consciously designed to perform in this fashion as discussed above.
Once the poker 12 has reached its assigned depth within the tailing mass, nose cone 32 is drawn upwards by the central pipe 37 and the paddles 14 are extended out into the surrounding tailings and, made to rotate. It is anticipated that this deployment will be accomplished by incremental adjustment of extension and rotation speed, determined by the “feel” of the machine operator. And, furthermore the operator's “feel” will be a component in determining the effective/efficient rate of withdrawal. Alternatively, it is obviously possible, by state-of-practice technology to utilize pressure sensors and solenoid instrumentation to have the apparatus operated remotely. Once extended, the paddles are alternated between rotation and vibration thereby mixing and packing the particulate (in this case tailings).
To treat large aerial extents, the columnar treatment proposed here would simply need to be applied at multiple interconnected positions across the area requiring treatment. The mining/design engineer would lay out an array of treatment axes suitable to optimize the operation.
The novel approach presented above is based on the realization that the pore spaces existing between larger particles are both filled with fluid and at the same time potential reservoirs for smaller particles or viscous fluids such as tailing slimes or cement grout or the like.
The apparatus is designed to be operated in two modes which may be employed separately or in combination. These modes are described separately below for clarity, and are referred to as the volume reduction mode, and the void space utilization mode.
The Volume Reduction Mode
In this mode, energy is expended in both strata mixing and vertical vibration.
Since the natural processes of fluid transport of particles (tailings are discharged as dense fluid into impoundment/storage/pond) results in particles settling out of suspension strictly according to their size and the lateral velocity of the transporting fluid; consequently, the resulting deposit of the solid phase is inherently a layering of uniformly sized particles. Furthermore, because the discharge from the mill is variable and episodic (rather than the relative constant flow of a river bearing a range of soil particles) the solid phase comes out of suspension in strata of uniform size which have limited areal extent. Thus, the typical tailings deposit consists of seams of uniformly sized particles (consequently of loose packing, and low density) with large pore volumes containing fluid. These seams are inter-layered to an extent which depends on the degree of mill discharge temporal consistency/inconsistency as well as the location at which the mine staff choose to position the discharge pipe around the perimeter of the pond.
The result is that the volume occupied by tailings is unnecessarily high because of being made up of seams of uniformly sized particles. The solution advocated here is to intentionally disturb these naturally formed seams, so that the particle sizes are mixed together in order that the volume occupied by the solid phase aggregation of particles is reduced as the pore space between larger particles becomes filled by smaller particles. This procedure will result in making the overall volume previously needed to store the separate seams of uniformly sized particles much reduced. And in consequence the fluid volume previously occupying the pore spaces will be liberated as a supernatant liquid which can be pumped back to the mill or for further treatment. The supernatant liquid is either collected at the surface level or can be collected within the outer casing 30 through drainage holes 56 and drawn to the surface by suction.
Mixing of grain sizes ensures that the resulting aggregation cannot liquefy. An important implication of this is that the treated tailings should thereafter allow the option for safe use of “upstream” construction above treated tailings. It is anticipated that the placement of a layer of earthfill (for an increase in tailings dam crest elevation) could commence within a week or so of treatment by the method and apparatus presented herein.
The Void Space Utilization Mode
In this mode energy is expended in pressurized fluid injection and in paddle rotation to spread the fluid further afield, and possibly in pumping fluid to the surface.
In addition to the general deployment equipment (the mobile carrier for land 2 being shown in
Referring to
At the bottom end of 37, within the compass of the paddles, (see
The fluid injection portion of the poker could be used to either fill the void space with tailing suspension (also referred to as yoghurt) so as to dispose of this waste in a suitable manner. Alternatively, by injecting a cement grout, a concrete column could be formed which would likely prove more economical than stone-column construction.
In an alternative embodiment shown in
Referring to
The cable cover 136, and cable 134 are located within the cylindrical drive shaft 138, the drive shaft extending from the rotation motor drive in the power box 8 to upper spiral coupling 44. A lower spiral coupling 48 is seated within bushing 50 and is freely rotatable and vertically retained therein. The various components may be made of any suitable material; for example, cable cover 136 may be made of mild steel pipe or tubing while the cable 134 may be made of steel rope.
The cable cover sleeve 136, which is connected to, and seated within, the lower spiral coupling 48, extends a sufficient distance upwards towards the power box 8 to prevent tailings or particles adhering to the hoisting cable 34 because of its initial immersion in the tailings/soil from contaminating the mechanism above the sealed bushing 50.
The plurality of deployable paddles 14 are hingedly connected at one end to the lower spiral coupling 48 and are hingedly connected at the other end to the nose cone 132.
The bottom portion of poker 112 is shown in
After insertion into the material to be treated to a desired depth, mixing paddles 14 are deployed. As shown in
In the alternative embodiment taught in
It will be appreciated by those skilled in the art that the preferred and alternative embodiments have been described in some detail but that certain modifications may be practiced without departing from the principles of the invention.
Number | Date | Country | |
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61882621 | Sep 2013 | US | |
62004402 | May 2014 | US |