Patent Application
20230398555
This invention relates to froth flotation cells, particularly froth flotation cells utilized for removing mineral values from ore slurries. The invention aims to prevent or discourage the formation of a slurry vortex within a standpipe of a froth flotation cell. Accordingly, embodiments described herein help to reduce surface instabilities at a pulp-froth interface inside the froth flotation cell.
Froth flotation cells are used to separate mineral values from mineral wastes. An ore is finely ground and suspended as a water-based slurry or pulp in a flotation cell. An impeller or rotor is turned at a high speed in the slurry to suspend the mineral particulates and to distribute or disperse air bubbles into the slurry. The mineral values attach to the air bubbles. The bubbles with the entrained mineral values then rise to form a froth atop the pulp or slurry pool. The froth overflows a weir and is collected in a launder for further processing. Some examples of flotation cells are described in U.S. Pat. No. 5,611,917 to Degner; U.S. Pat. No. 4,737,272 to Szatkowski et al.; U.S. Pat. No. 3,993,563 to Degner; U.S. Pat. No. 6,095,336 to Redden et al.; and U.S. Pat. No. 6,070,734 to Hunt et al.
As depicted in
The instability of the slurry vortex 6 varies the degree of submergence of the rotor 4 and produces a fluctuating air-inflow rate. As a result, multi-phase jet characteristics such as void fraction and velocity become unstable. The unstable jet stream generates waves at the pulp-froth interface 8 within the tank of the froth flotation cell and makes the level of the pulp-froth interface 8 sway periodically. These waves (and swaying action) can make it difficult to control the pulp-froth interface 8 level and operate froth flotation cells in applications where the froth height is relatively low. The waves generated can allow the pulp below the pulp-froth interface 8 to splash into the launder and negatively impact flotation machine performance. It is also desirable to be able to set a pulp-froth interface 8 level and control its location because this has an effect on the grade and recovery of the flotation device. When the surface is unstable, the level of height of the pulp-froth interface 8 varies, and, as a result, this parameter can be difficult or near impossible to set, change, or control.
Some attempts have been made to mitigate the negative effects of slurry vortex formation 6 within a froth flotation cell. For example, a standpipe design (shown in WO 2013/067343), aims stabilize a slurry vortex 6 by placing curved baffle surfaces within inner surfaces of a standpipe to counteract slurry flows within the standpipe. The present invention, as will be appreciated hereinafter, seeks a completely different mechanism to counteract slurry vortex 6 formation/instability.
An aim of embodiments of the present invention is to provide an improved froth flotation cell 100 wherein a slurry vortex 6 forming in the standpipe 2 may be stabilized and/or prevented from forming, without limitation.
Another aim of embodiments of the present invention is to provide improved apparatus for preventing a slurry vortex 6 from affecting pulp or slurry movements within the tank 112 of a froth flotation cell 100, thereby improving machine performance and recovery, without limitation.
Yet another aim of embodiments of the present invention is to provide improved apparatus for preventing or discouraging the ingress of slurry into a standpipe 152 from a froth flotation cell tank 112 during operation, without limitation.
Yet another aim of embodiments of the present invention is to provide improved apparatus for minimizing the amount of mass and/or volume of slurry that can remain in a standpipe 152, without limitation.
Yet another aim of embodiments of the present invention is to provide improved apparatus for minimizing height changes and non-stable dynamic movements of slurry within a standpipe 152, without limitation.
A further aim of embodiments of the present invention is to provide an apparatus (e.g., slurry vortex stabilizer 166) that may be easily retrofitted into existing froth flotation cells to help quell, diminish, or eliminate problematic wave formations of pulp or slurry within a froth flotation cell tank 112 that are caused by the formation of a slurry vortex 6 within a standpipe 152 during froth flotation cell operation.
A related aim is to provide stabilizing structures which more effectively combat detrimental effects associated with slurry vortex 6 formation and movement, and which demonstrate increased performance over prior designs intended for stabilizing a slurry vortex 6 in a froth flotation cell (e.g., such as the standpipe design shown in WO 2013/067343), without limitation.
A slurry vortex stabilizer 166 is disclosed. A self-aspirated froth flotation cell 100 may comprise the slurry vortex stabilizer 166. The slurry vortex stabilizer 166 may be configured for placement within a tank 112 of a self-aspirated froth flotation cell 100. The slurry vortex stabilizer 166 may, for instance, be configured for placement above a rotor 114 of the self-aspirated froth flotation cell 100, without limitation. The slurry vortex stabilizer 166 may be configured to surround a drive shaft 142 supporting and driving rotation of the rotor 114.
The slurry vortex stabilizer 166 may comprise an annular body 234. The annular body 234 may have an upper annular edge 176. The annular body 234 may have an aperture 180 extending through a central region of the annular body 234. The aperture 180 may have an inner surface 182 bounded between an upper inner edge 178 and a lower inner edge 200. The inner surface 182 may be configured to allow the drive shaft 142 to rotate freely therein, in close proximity to the inner surface 182.
An annular undersurface 210 of the slurry vortex stabilizer 166 may comprise an inner first portion 212 and a second portion 236. The second portion 236 may be provided around the first portion 212. An annular intersection, transition, or inflection 214 may be provided between the first 212 and second 236 portions. The annular undersurface 210 of the annular body 234 may be configured to be provided radially-inwardly of a disperser hood 136 in the self-aspirated froth flotation cell 100.
The slurry vortex stabilizer 166 may further comprise a sloped upper surface 242. The sloped upper surface 242 may taper downwardly towards the central region of the annular body 234 as it approaches the aperture 180. The first portion 212 may be located radially-inwardly of the second portion 216 with respect to an axis of rotation 118 of the drive shaft 142 and/or rotor 114. The first portion 212 may be located closer to the aperture 180, lower inner edge 200, and/or inner surface 182 of the aperture 180 than the second portion 216. In some embodiments, the sloped upper surface the annular body 234 may be configured to be provided radially inward of surfaces of a disperser 134 or disperser hood 136 within the self-aspirated froth flotation cell 100.
The aperture 180 may extend concentrically through the annular body 234. For example, radial distances between the upper inner edge 178 and upper annular edge 176 may be equidistant around the slurry vortex stabilizer 166.
In some embodiments, the sloped upper surface 242 may comprise a concave dished upper surface 174. For example, the sloped upper surface 242 may comprise a frustospherical surface. The sloped upper surface 242 may, in some embodiments, comprise an angled floor 222. The angled floor 222 may comprise a faceted surface (e.g., a flat planar surface), a frustoconical surface, a frustospherical surface, a concave surface, a dished surface, or a combination thereof, without limitation.
The first portion 212 may comprise a convex, frustospherical, or frustoconical surface. The second portion 236 comprises a concave, dished, or tapered surface. The concave, dished, or tapered surface may narrow towards (i.e., as it approaches) the intersection or transition 214.
The slurry vortex stabilizer 166 may comprise a number of webs 218 extending upwardly from the sloped upper surface 242. For example, each web 218 may define at least one interface 230 (e.g., intersection, transition, or corner region) between a sloped upper surface 242 and a surface of the respective web 218.
Webs 218 may be provided between (e.g., extend between) the upper annular edge 176 (or upper annular rim 226) and an external wall 224 of a central hub 220. At least one interface 228 may be defined between the external wall 224 of the central hub 220 and a portion of the sloped upper surface 242 (e.g., an angled floor 216). The central hub 220 is preferably tubular and has a cylindrical shape (e.g., defined at least in part by the inner surface 182 of aperture 180 and the external wall 224), without limitation.
If present, the webs 218 may extend at any angle with respect to a tangent of the external wall 224 or with respect to a surface of the sloped upper surface 242. Webs 218 may also be skewed, offset (e.g., radially), curved, or slanted in any one or more of the axes D, 118, 118′, 118″, without limitation. As shown, the webs 218 may extend radially with respect to the body 234 and toward a center of aperture 180, and extend orthogonally upward from the sloped upper surface 242, without limitation.
The slurry vortex stabilizer 166 may comprise a disperser hood 136. The disperser hood 136 may be integrally provided to the slurry vortex stabilizer. For example, the slurry vortex stabilizer 166 and disperser hood 136 may share the same monolithic and unitary structure, such that the two may not be separable from one another.
The slurry vortex stabilizer 166 may comprise an upper collar 184. A gap 190 may be present between an outer peripheral surface 188 of the annular body 234 and the upper collar 184 of the disperser hood 136. The gap 190 may be configured for receiving a lower portion of a standpipe 152 that is positioned within the self-aspirated froth flotation cell 100. The upper collar 184 may comprise at least one mounting feature 194 for mounting the upper collar 184 to the standpipe 152.
The disperser hood may comprise a lower bell 196. The lower bell 196 may extend downwardly and radially-outwardly from the upper collar 184. The lower bell 196 may comprise an upper bell surface 202, a lower bell surface 208, and a lower outer peripheral surface 206. A number of perforations or openings 204 may extend through the upper 202 and lower 208 bell surfaces and through the lower bell 196. The upper bell surface 202 and lower bell surface 208 may be frustoconical as shown, but may have a dished or other shape, without limitation.
The sloped upper surface 242 of the body 234 may be configured to form a lower fluid boundary surface within the standpipe 152. One or more mounting features 232 for securing the annular body 234 to a separable detachable disperser hood 136 and/or to a separable detachable disperser 134. The slurry vortex stabilizer 166 may be configured for attachment to both the disperser 134 and disperser hood 136 via the one or more mounting features 232. The body 234 of the slurry vortex stabilizer 166 may be located radially inward from the disperser 134. The disperser 134 may surround an outer peripheral surface 188 annular body 234.
In some embodiments, the upper collar 184 may be modular. For example, the upper collar 184 may comprise an upper portion 184a defining a portion of a disperser 134, and a lower portion 184b defining a portion of a disperser hood 136. In such embodiments, the upper portion 184a may be separable from the lower portion 184.
A method of performing a flotation operation is also disclosed. The method operation may comprise the step of providing a slurry vortex stabilizer as described above within a tank 112 of the self-aspirated froth flotation cell 100, around the drive shaft 142 and/or above the rotor 114 such that the inner surface 182 of the aperture 180 surrounds the drive shaft 142. The method may further include the step of rotating the rotor 114 and drive shaft 142 while slurry is held within the tank 112. The method may further include the step of drawing air into the slurry within the tank 112. The method may further include the step of preventing the formation of a slurry vortex 6 or waves in the slurry in the tank by virtue of the provision of the slurry vortex stabilizer 166 within the tank 112.
As illustrated in
A lower end of the rotor 114 may be juxtaposed to an upper end of a draft tube assembly 110. As shown, the lower end of rotor 114 may be juxtaposed to an upper end of a cylindrical draft tube extension (i.e., spacer element) 125, which is coupled at a lower end thereof to a conical draft tube 126. Conical draft tube 126 may be spaced from a lower wall or panel 128 of tank 112 by a plurality of supports 130. Supports 130 may define a plurality of openings 132 through which pulp or slurry can move into the conical draft tube 126. During operation, the pulp or slurry is drawn through the openings 132 and into the conical draft tube 126, up the cylindrical draft tube extension 125, and towards the rotor 114. By virtue of surfaces of the rotor 114 (and/or vanes 116) being disposed within and/or in close proximity of the draft tube 110, the rotor 114 may act to pump the pulp or slurry through the openings 132, upwardly into the draft tube 110, and then radially outwardly (e.g., through an optional stationary fenestrated disperser 134 and/or disperser hood 136) along general direction 7, without limitation.
An upper end of the rotor 114 may be surrounded by an optional stationary fenestrated disperser 134. The disperser 134 may be tubular in design and preferably arranged to be coaxial with rotor 114. When employed, disperser 134 may serve to facilitate shearing of air bubbles formed by rotation of the rotor 114 and/or to reduce the energy after mixing of air and pulp. Positioned over and/or circumferentially about the disperser 134 (where used) and surrounding rotor 114 may be a perforated conical disperser hood 136 for stabilizing the pulp surface. The disperser hood 136 may at least partially envelop or surround upper outer portions of the disperser 134 and/or rotor 114 as shown in
Rotor 114 may be operatively connected to a motor 140 via a drive shaft 142, one or more transmission belts 144, and one or more sheaves 146 and 148 as depicted in
The tank 112 of the froth flotation cell may be provided along an upper end thereof with a froth overflow weir (i.e., launder) 160 which is configured to receive froth and channel it away from the froth flotation cell 100. A pipe 162 (e.g., galvanized pipe) and one or more nozzle elements 164 provided thereto may be provided to the froth flotation cell for delivering cleaning fluid and spraying/washing/cleaning froth in launder 160. Optionally, one or more nozzle elements 164 may be provided to the pipe 162 for cleaning froth at various locations around the top of tank 112, without limitation.
A standpipe 152 may be mounted at least partially inside tank 112 proximate an upper end of the rotor 114. The standpipe 152 facilitates ingesting of air in to pulp or slurry within tank 112 by virtue of rotor 114 spinning along axis 118. As air is ingested into standpipe 152, a fluctuating height slurry vortex 6 traditionally develops within standpipe 152 as described in the background of this description and depicted in
For example, during operation of the froth flotation cell 100, as the drive shaft 142 rotates (see arrow 170), a slurry vortex 6 with a somewhat upward velocity vector 172 may form. To combat this, a slurry vortex stabilizer 166 according to the invention is provided below and/or within the standpipe 152, above the rotor 114 and around the drive shaft 142. The slurry vortex stabilizer 166 may, in some embodiments, be positioned, for example, between a disperser 134 and the standpipe 152, radially inward of the disperser hood 136, without limitation. The slurry vortex stabilizer 166 serves to combat the formation of the slurry vortex 6 in the first place, control and mitigate movement and fluodynamic effects of a formed slurry vortex 6, and/or combat disruptions to pulp or slurry within the tank 112 which might be caused by consequential dynamic movements of the slurry vortex 6, without limitation.
By virtue of its design, the slurry vortex stabilizer 166 may be configured to substantially fluidly-isolate the region inside of the standpipe 152 from contents within the tank 112 (e.g., pulp or slurry). Embodiments of the slurry vortex stabilizer 166 may be uniquely adapted to discourage slurry or pulp within tank 112 from migrating upward into the standpipe 152 by virtue of its body 234, thereby providing a substantial physical barrier between the drive shaft 142 and inner fluid boundaries of the standpipe 152. By minimizing the amount of tank 112 contents that can move up into the standpipe 152 from the tank 112 (via a tortuous path between the slurry vortex stabilizer 166 and rotating drive shaft 142), the overall mass and/or height of any slurry vortex 6 that can be generated in the standpipe can be controlled, minimized, or eliminated entirely. Said differently, in the presence of the novel slurry vortex stabilizer 166 described herein, the mass or volume of slurry that may be able to find its way into and/or remain within the standpipe 152 during froth flotation cell 100 operation will have a much-reduced negative impact on overall fluid dynamic environments occurring within the tank 112. For example, any fluctuations in height of a diminished slurry vortex 6 present in the standpipe 152 will have less ability to form disruptions such as waves within tank 112 due to a lesser possible hydrostatic head pressure and/or downward slurry momentum.
Slurry vortex stabilizer 166 may be made integral (i.e., monolithic with) a disperser hood 136 as shown in
A slurry vortex stabilizer 166, according to embodiments of the invention, may comprise a body 234 having a sloped upper surface 242, an annular undersurface 210, and an outer peripheral surface 188. An upper annular edge 176 may surround the sloped upper surface 242 and define an upper peripheral edge of the body 234. In some embodiments (
The annular undersurface 210 may comprise a first portion 212 and a second portion 236 separated by an intersection, transition, or inflection 214 therebetween. The first portion 212 and second portion 236 may have different surface shapes and/or profiles, without limitation. The first portion 212 may comprise a protruding surface, for example, a convex, frustospherical, or frustoconical surface, without limitation. The second portion 236 of the annular undersurface 210 may comprise a concave, dished, recessed, or tapered surface, without limitation. The first portion 212 may be surrounded by the second portion 236 and more proximate to the aperture 180.
In some embodiments (
In some embodiments (e.g., as shown in
In any of the embodiments disclosed herein, disperser hood 136 may comprise a lower bell 196 (e.g., flared frustoconical flange) extending radially outwardly and downwardly from the upper collar 184 from a collar-bell intersection 198. The lower bell 196 may therefore be provided below upper collar 184 and extend therefrom proximate the collar-bell intersection 198. The lower bell 196 may comprise an upper bell surface 202, a lower bell surface 208, a lower outer peripheral edge defining a radially-outermost profile or periphery of the lower bell 196, and perforations or a number of openings 204 extending through the lower bell 196 and its upper 202 and lower 208 surfaces.
In some embodiments, one or more mounting features 232 may be provided to the outer peripheral surface 188 of the body 234. Each of the mounting features 232 may comprise an aperture or hole for securing a fastener (e.g., bolt, pin, screw) to an optional disperser 134 and/or disperser hood 136. In such embodiments, one or more mounting features 240, 244 (e.g., aperture, hole) aligned and complimentary with mounting features 232 may be provided to the disperser 134 and disperser hood 136, respectively. A fastener, such as a bolt, pin, or screw (not shown) may engage the mounting features 232, 240, 244, to secure the slurry vortex stabilizer 166, disperser 134, and disperser hood 136 together. While not shown, the disperser 134 may be omitted from the assembly such that the disperser hood 136 may be coupled directly to the body 232 of the slurry vortex stabilizer 166 via mounting features 232, 244 in the absence of a disperser 134 therebetween.
It should be understood that in some embodiments, while not shown, the disperser 134 may be optionally omitted from the froth flotation cell 100 and slurry vortex stabilizer 166/disperser hood 136 assembly. It should further be understood that while not shown, in some embodiments, disperser hood 136 may comprise a number of vanes (e.g., radially-inwardly and downwardly-extending scalloped vanes) extending from lower bell surface 208. The vanes extending from the lower bell surface 208 (not shown) may comprise, for example, those shown and disclosed in Applicant's co-pending patent application U.S. Ser. No. 62/975,475 filed 12 Feb. 2020, which is incorporated by reference in its entirety, for any and all purposes, as if fully set forth herein.
Turning to
A number of webs 218 may extend between the annular upper rim or projection 226 and the central hub 220 as shown. The webs 218 may, according to some non-limiting embodiments, may comprise triangular, radially-extending, stationary vanes, without limitation. The webs 218 may be skewed, curved, slanted, obliquely-arranged, offset, or canted with respect to: the rotational axis 118, a radial direction 118′, or a direction 118″ which is transverse to the radial direction 118′ (e.g., a tangential direction), without limitation.
The webs 218 may define a number of upper pockets 216 therebetween. Each upper pocket 216 may be defined between surfaces of webs 218, an angled floor 222, and the external wall 224 of the central hub 220. A hub/floor interface 228 may define a lower corner edge of an upper pocket 216 in a radial direction along the angled floor 222, without limitation. A web/floor interface 230 may define a lower corner edge of an upper pocket 216 in a direction 118″ which is transverse to the radial direction 118′ (e.g., a tangential direction) along the angled floor, without limitation.
Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention.
Nomenclature and technical terms used in this description and the claims to define features has been chosen for convenience, and it should be understood that specific terms used herein may be replaced with art-recognized equivalents. For example, while the term “slurry vortex stabilizer 166” has been arbitrarily chosen and used consistently throughout this specification and in the claims, this term could be obviously replaced with similar terms like “vortex stabilizer,” “stabilizing structure,” “vortex prevention means,” “structure for preventing slurry vortex formation,” “structure for mitigating effects of slurry vortex formation,” “standpipe isolation device,” “standpipe seal,” “baffle between standpipe and drive shaft,” “sealing structure,” “slurry wave prevention apparatus,” and the like, without departing from the scope and spirit of the invention.
Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/059361 | 10/12/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63090309 | Oct 2020 | US |
