Classifying – separating – and assorting solids – Fluid suspension – Liquid
Reexamination Certificate
1998-04-09
2001-10-30
Lithgow, Thomas M. (Department: 1724)
Classifying, separating, and assorting solids
Fluid suspension
Liquid
C261S087000, C261S093000, C366S102000, C366S317000
Reexamination Certificate
active
06308834
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an impeller primarily but not exclusively for use with apparatus adapted to enhance mixing of a gas and a liquid, as used for example in froth flotation apparatus for separation of substances.
DESCRIPTION OF THE PRIOR ART
Froth flotation is a process currently used in both mineral processing to separate required mineral particles from gangue in a mineral ore slurry and in other processing systems when a separation of one liquid type or types can be made from another liquid or liquids. The apparatus utilised comprises a tank for holding the slurry, an impeller for inducing flow of the slurry and dispersing a gas therein, a static diffuser arrangement located outwardly of the impeller and a means to introduce the gas, commonly compressed air, into the slurry.
It will be appreciated that the term “mixing” used herein should be read as relating to dispersion of a gas in a liquid, true homogeneity not necessarily being achieved by introduction of the gas into the liquid. Furthermore, the term liquid will hereinafter he used although it will be appreciated that during use of the apparatus the liquid may contain solid matter and thus constitute a slurry, and the term slurry should be understood to comprise a suspension of solid particles in a liquid in general, and not be limited to any particular mineral suspension.
The mechanism of the extraction process is known in the art, and will therefore not be described here in any great detail, although an outline of the principal when used in mineral processing is to cause the required mineral particles to adhere to bubbles of the gas, which then rise to the surface of the liquid to form a froth which is removed. A plurality of such tanks may be provided in series with the liquid passing through each in turn, such that any required minerals not extracted in a given tank may be subjected to a further extraction process in the next tank in the series, or a single tank housing a plurality of gas/liquid mixing apparatus may he provided.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved impeller which enhances the above mixing process and improves the efficiency of the extraction process.
According to a first aspect of the invention there is provided an impeller for rotation about a substantially upright axis for use with apparatus adapted to enhance mixing of a gas and a liquid, the impeller having a substantially upright portion substantially parallel to the axis, and a plurality of vanes extending outwardly therefrom, at least some of the vanes having an upper part adapted to induce liquid flow generally downwardly towards the impeller and a lower part adapted to induce liquid flow generally upwardly towards the impeller, wherein the impeller further comprises barrier means at least partially dividing said upper and lower parts, and a gas input situated on the same side of the barrier means as the lower part.
Preferably, the barrier means extends outwardly from the substantially upright portion.
The barrier means preferably comprises a flange-like member having upper and lower faces, at least one face of which is flat or substantially flat. Preferably the lower face is the flat or substantially flat face.
Preferably the flange-like member is substantially planar. Conveniently the flange-like member lies in a plane substantially perpendicular to the axis of rotation. The flange-like member may conveniently be disc shaped.
The substantially upright portion may comprise a cylinder-like portion wherein the vanes extend outwardly from the outer surface of the cylinder-like portion. Conveniently, the vanes extend radially outwardly from the cylinder-like portion. The vanes may be secured to the outer surface of the cylinder-like portion, or may pass partly therethrough.
The substantially upright portion preferably has at least one passage therein. Conveniently, the or each passage lies substantially parallel to the axis of rotation of the impeller.
A lower end of the substantially upright portion is preferably located below the plane of the barrier means.
Conveniently, the or each passage has an input end adapted to receive at least one gas and an output end adapted to emit the or each gas to the tank. Preferably the input end is adapted to be connected, in use, to a gas source which is at greater than atmospheric pressure.
Conveniently, the output end is situated at or near the lower end of the substantially upright portion.
As an alternative, the substantially upright portion may be substantially hollow. Preferably the substantially upright portion comprises a tube. The tube may also have an input end and an output end analogous to those described above.
Conveniently, only a part of the vanes engage the substantially upright portion.
The barrier means preferably comprises an annulus, the inner rim of which is located substantially adjacent the outer surface of the tube. Conveniently, the radius of the annulus is less than the dimension of the vanes in a radial direction. Such a direction will henceforth be referred to as the width of the vanes, and, correspondingly, the dimension perpendicular to the width, and thus parallel with the axis of rotation of the impeller, will be referred to as the height.
The upper part of the vanes preferably has a top edge and inner and outer side edges, wherein the inner side edge abuts or passes into the substantially upright portion, and wherein the outer side edge is remote from the substantially upright portion. The outer side edge of the upper part sweeps through the liquid in the tank in a rotational manner in order to induce flow of the liquid. The top edge of the vane and the outer side edge of the upper part of the vane may meet substantially at right angles to each other to define a corner of the vane.
Alternatively however, the top edge of the vane and the outer side edge of the upper part of the vane may be joined by an intermediate edge.
The intermediate edge may be generally linear, or may be of curved configuration. Preferably, the curved configuration is concave.
The lower part of the vane has a bottom edge, and inner and outer side edges. Preferably, the inner side edge is located at or near the axis of rotation. Accordingly, where there are a plurality of such vanes, the inner side edges of each preferably meet at or near the axis of rotation.
There is preferably an intermediate edge between the bottom edge and outer side edge of the lower part of the vane. Conveniently, the intermediate edge is of curved configuration suitable to induce flow of the liquid generally upwardly towards the impeller. Preferably, the curved configuration is concave.
Alternatively, the substantially upright portion may comprise a cylinder-like portion wherein the vanes extend outwardly therefrom but do not engage the outer surface of the cylinder-like portion. In such a case, the cylinder-like portion may have associated therewith a flange, henceforth referred to as a drive flange for the sake of clarity. The drive flange is preferably of annular configuration. Preferably, the barrier means is attached to or integral with the drive flange. In this alternative, the barrier means comprises a first part attached to or integral with the drive flange, and a second part extending radially outwardly from the first part.
Preferably, the second part engages at least some of the vanes. Preferably, both the first and second parts are substantially annular, having substantially flat lower faces. In this alternative, the distance between opposite inner side edges of the upper parts of the vanes is preferably greater than the diameter of the cylinder-like portion. Conveniently, said distance is greater than the diameters of both the drive flange and the first part of the barrier means. The inner side edges of the lower parts of the vanes, in this alternative, do not meet at or near the axis of rotation. There is preferably provided a central portion which engages said inner side edges.
Conveniently, the central portion comprises a cylinder, the
Peaker Richard Asheton
Schlittler William John
Svensson Ulf Krister
Trudel Joseph Rene
Kinney & Lange , P.A.
Lithgow Thomas M.
Svedala Limited
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