Classifying – separating – and assorting solids – Stratifiers – Elements
Patent
1990-10-11
1992-09-22
Hajec, Donald T.
Classifying, separating, and assorting solids
Stratifiers
Elements
209491, 209503, 209437, B03B 504, B03B 1300
Patent
active
051489228
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a separator for the separation of heavier particles (usually metallic ore) from lighter waste material, or alternatively for the separation of larger particles from smaller ones. It relates for instance to a so-called "gravity" system of separation, in which the separation is accomplished by applying a slurry on to a sloping surface, and shaking the surface, thereby causing the heavier or larger particles (which tend to sink faster than the lighter or smaller waste particles) to be preferentially retained upon the surface, while the lighter particles flow off to waste. The invention is particularly effective (when compared with the prior art) in the separation of small particles.
BACKGROUND OF THE INVENTION
The general idea of separating particles using a vibrating inclined surface to which a slurry is applied is already known, for example from NRDC's British Patent Specification 1576469. This shows that it is known to suspend from a framework an assembly of vertically-spaced inclined decks to the upper edges of which a feed of the slurry is supplied while the decks are vibrated. A subsequent water wash removes separated ore particles which have collected on the decks.
This patent is merely exemplary of a number of known separators known as "gravity" separators. The common feature of all of these is a vibrating surface or deck. Some devices have provision for a continuous flow of material to be treated, while others operate on a series of cycles. It is particularly (though not exclusively) to devices of the latter class to which the present invention relates.
The standard nomenclature for this type of device is as follows. The separation surface is called a deck; in practice several such decks are often used at once, one above the other. The slurry of material fed to the deck for separation is called the feed. The heavy particle material to be collected as the finished product is called the concentrate; the actual proportion of heavy particles within this concentrate may vary considerably: when the device shown in GB1576469 is used to separate tin particles, the feed might typically consist of 1% tin, whereas the tin content of the concentrate from the device of the present invention might typically be 25% tin. The material collected for reprocessing and/or recirculation is called the middlings. The waste material, containing a low proportion of heavy particles is called the tailings.
Details of the cycling type of separator will now be described. A single cycle of such a separator consists of a feed stage, a wash stage, a middlings flush stage and a concentrate flush stage. A single cycle takes, for example, typically 8 minutes.
During the feed stage which takes approximately 4 minutes, the feed material is fed across the full width of the upper end of the sloping shaken deck so that it flows slowly down over the surface forming a layer of perhaps 2 mm to 5 mm deep. Much of the lighter waste material flows off the lower end of the deck during this period, but perhaps half still remains mixed with the heavier particles.
At the end of the 4 minute period, the feed is turned off and the washing commences. During this stage, wash water is fed from the upper end of the deck, which continues to be shaken. The washing action tends to assist in the separation process of the material on the deck; as the washing continues, the surface at the upper end of the deck largely clears of all the waste material, and leaves behind only the heavy concentrate. This clearance of most of the material continues slowly and progressively down the length of the deck. Thus, as one looks at the deck during the washing process, one can see that waste material is being cleared from the deck starting at its upper end with the edge of the cleared section being distinctly visible as a relatively broad band of change from lesser to greater density which moves slowly down the deck.
It will be appreciated that the upper end of the deck tends to collect little material, but including
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patent: 4795552 (1989-01-01), Yun et al.
patent: 5024334 (1991-06-01), Hisra et al.
patent: 5028317 (1991-07-01), Lyman
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