Classifying – separating – and assorting solids – Fluid suspension – Liquid
Patent
1993-05-24
1997-01-07
Lithgow, Thomas M.
Classifying, separating, and assorting solids
Fluid suspension
Liquid
2102212, 210220, 261 76, 261123, B03D 124, B01F 304
Patent
active
055913288
DESCRIPTION:
BRIEF SUMMARY
The present invention relates no a method and apparatus for gas particle formation in liquid media and relates particularly, though not exclusively, to aeration of a liquid/slurry in flotation apparatus.
BACKGROUND TO THE INVENTION
The method and apparatus for gas particle formation according to the invention can be used in any application requiring efficient aeration of liquid media such as, for example, aeration/oxygenation for biological waste liquid purification using aerobic micro-organisms, liquid/slurry preaeration and/or combined shear flocculation, liquid gasification and suspension of minerals or coal enrichment. The following description will be given with particular reference to gas particle formation and dispersion in a liquid/slurry in mineral flotation apparatus, however it will be appreciated that the inventive method and apparatus has much wider applications.
Froth flotation is a process used for concentrating values from low-grade ores. After/during fine grinding the ore is mixed with water to form a slurry. Chemicals are added to the slurry to preferentially develop differences in surface characteristics between the various mineral species present. The slurry is then copiously aerated and the preferred (hydrophobic) mineral species cling to bubbles and float as a mineralised froth which is removed for further processing.
It is well established that a key factor in the performance of the flotation technique is the size, volume and distribution of gas particles or air bubbles that can be dispersed into the slurry. The present invention was developed with a view to providing a method and apparatus for gas particle formation in which the desired size of gas particles can be readily controlled and a relatively uniform distribution of gas particles can be achieved irrespective of the gas flow rates required by the process. Several further improvements to flotation apparatus are also described.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of gas particle formation in a liquid medium comprising the steps of: medium; directed towards said edge; as it approaches and/or escapes from said edge.
Preferably the method further comprises generating a second flow of liquid which converges with the first mentioned flow at said edge.
Typically the first and second liquid flows have dissimilar velocities and are typically accelerated towards the edge of the surface together with the gas film.
According to another aspect of the present invention there is provided an apparatus for gas particle formation, the apparatus comprising: thereto when submerged in a liquid medium; said surface having an edge arranged so that, in use, a flow of liquid generated over said surface, adjacent said film of gas, and directed towards said edge results in the gas film being broken into gas particles by shear forces as it approaches and/or escapes from said edge.
Preferably said edge is in the form of a lip whereby, in use, said flow of liquid over said surface can converge with a second flow of liquid at said lip.
In one embodiment of the apparatus said structure comprises a cylindrical body having a circumferential edge flared outwardly defining an annular lip at one end, an outer surface of said body being adapted to form said film of gas thereon. Preferably said body is housed in a chamber having a liquid inlet and having an outlet in the form of a circular aperture with an inner escape diameter slightly larger than an outer diameter of said annular lip.
In an alternative embodiment said structure comprises first and second hollow bodies mounted concentrically within a chamber such that outer circumferential edges of the bodies form at least one annular gap through which liquid and gas can escape. Preferably an outer surface of at least one of said hollow bodies is adapted to form said film of gas thereon. Preferably the chamber is provided with a cylindrical wall having a peripheral edge that forms an annular gap with an outer circumferential edge of one of the
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Atomaer Pty. Ltd.
Lithgow Thomas M.
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