Classifying – separating – and assorting solids – Stratifiers – With liquid treatment
Patent
1982-11-17
1984-10-16
Scherbel, David A.
Classifying, separating, and assorting solids
Stratifiers
With liquid treatment
209697, 209493, B03B 552
Patent
active
044769806
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to an improved spiral separator and to a method of spiral separation which are of particular use in the separation of minerals.
BACKGROUND ART
Spiral separators are extensively used for the wet gravity separation of solids according to their specific gravity, for example for separating various kinds of mineral sands from silica sand.
Separators of the kind under discussion commonly comprise a vertical column about which there are supported one or more helical troughs.
Reference herein to "cross section" in relation to a trough means, unless the contrary is expressed, a cross section taken in a vertical plane extending radially from the helix axis.
Each trough has a floor situated between an outer trough wall and an inner trough wall. As herein used, the expression "Working surface" means that portion of the trough floor which in use supports pulp or solids. The expression "working surface profile" means any profile of the working surface viewed in a cross section taken in a vertical plane extending radially from the helix axis. The trough working surface profile generally inclines upwardly and outwardly, from the radially inner wall or column towards the radially outer wall. In some separators the column may be, or may be a part of, the inner trough wall. It will be understood that the trough floor at, or adjacent to, the radially innermost end of the working surface profile may curve inwardly upwards to blend with the inner wall or column. Likewise at or adjacent to the radially outermost end of the working surface profile, the floor may curve upwardly to blend with the outer wall. The radially inner and outer walls serve to retain materials but generally play no role in the separation process.
In operation of such separators, a "pulp" of slurry of the materials to be separated and water is introduced to the upper end of a trough at a predetermined rate and as the pulp descends the helix, centrifugal forces act on less dense particles in a radially outwards direction while denser particles segregate to the bottom of the flow and after slowing through close approach to the working surface gravitate towards the column. The streams are separated at intervals by adjustable splitters, the mineral fractions to be recovered being carried away through take off openings associated with the splitters.
In the most usual form of spiral separator a number of adjustable splitters are employed along the length of each helix with the section of trough between each splitter and the next being essentially identical with the section of trough between any other splitter and the next. Some of the heavier mineral is separated in each trough section and removed by the subsequent splitter. To assist the removal of low specific gravity particles from the underlying high specific gravity particles it is often necessary to supply from a separate system a small amount of water flowing radially outwards. This is normally referred to as wash water. Both the splitters and wash water systems may require periodic adjustment. Commonly two or three helices are supported by the column each with a number of splitters and each helix is mounted so that the starts are equiangularly spaced about the column and as close as practicable to coplanar to facilitate the simultaneous feed of pulp to all three.
Separators of the kind described above are inherently expensive to manufacture and require a high degree of supervision in operation to achieve acceptable results.
DISCLOSURE OF INVENTION
Preferred embodiments of the present invention permit the segregation and separation of the heavier particles of a pulp and their separation from lighter particles to proceed with a reduced need for periodical removal of heavy particles via a splitter. The number of splitters required per trough is thus greatly reduced. In addition, preferred embodiments permit thin films of the water originally present in the pulp to flow with a radially outwards component in the areas in which light particles overli
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Foster Glenn B.
Mineral Deposits Limited
Scherbel David A.
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