Classifying – separating – and assorting solids – Stratifiers – With liquid treatment
Patent
1988-12-22
1991-07-02
Hajec, Donald T.
Classifying, separating, and assorting solids
Stratifiers
With liquid treatment
209489, 209491, 209496, B03B 524
Patent
active
050283170
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to the control of jig separators used for the beneficiation of minerals. In particular, the invention is directed to an apparatus for measuring the properties of the jig bed. The information derived from the measurements can be used to provide a continuous control signal to improve the operating efficiency of the jig separators by better regulation of the jig operating parameters.
Throughout the specification the term "minerals" should be employed to include such material as coal, tin ores, gold ores, iron ores, manganese ores and such other valuable materials as can be separated from less valuable materials by gravity concentration. The term "jig" is to be interpreted to means any device using a pulsating fluid to produce stratification according to particle specific gravity in a bed of broken mineral. In usual circumstances the jig treats a continuous flow of mineral and is provided with means for continuous or intermittent discharge of the lower specific gravity and higher specific gravity fractions of the mineral mixture.
(2) Prior Art
The accepted principles of jig operation are described by Wills (B. A. Wills, Mineral Processing Technology, 2nd Edition, Pergamon Press, 1981). Gaudin (A. M. Gaudin, Principles of Mineral Dressing, McGraw Hill, 1939) also discusses the physics of jig operation and means of control of discharge of dense material from jigs.
There are two requirements for efficient jig operation, namely (i) control of heavy product discharge from the jig, and (ii) control of the stratification of the mineral bed in the jig. The term stratification generally refers to the variation in particle density as a function of vertical position in the jig bed in the compacted or closed state. Assuming that the discharge of the dense material is correctly performed, the separation effected by the jig will be more efficient if the stratification is such that the dense mineral and less dense mineral components are present in distinct layers, facilitating discharge of either layer from the jig. If more dense, material is discharged at too high a rate from the bed in a jig compartment, the stratification profile will be altered and it will become impossible to maintain either the desired separation or the efficiency of separation. The desired separation in a jig compartment can be quantitatively described by the jig separation specific gravity SG.sub.50. SG.sub.50 is the density of those mineral particles which are recovered at equal mass flow rates in both the dense and less dense product streams from the compartment.
Various means of regulation of SG.sub.50 are known. They all involve making an indirect measurement of jig bed characteristics combined primarily with feedback control of the discharge of dense mineral from the jig, or less commonly, with manipulation of the jig operating parameters.
Most commonly, a so-called "float" is suspended in the bed by a vertical rod, or similar arrangement and the position of the float is sensed by electro-mechanical means. The float is usually a suitably shaped (e.g. "streamlined") body which, by use of weights can be caused to have a chosen or adjustable effective specific gravity. The float is usually intended to indicate the position of the top of the layer of most dense mineral in the bed. By maintaining the position of the top of the latter layer constant through regulation of discharge of the most dense mineral layer, it is intended that the SG.sub.50 for the jig shall remain constant.
In addition to the use of floats, it is also known to use pressure sensors to indicate the hydrostatic pressure at one or more points in the jig bed. The pressure signals can be interpreted to indicate the average specific gravity of the bed as a whole or the depth of the bed or the average specific gravity of the bed in a chosen zone of the bed.
In the control of bed depth or specific gravity, it must be recognised that the jig operates in a cyclical way due to the regular pulsation of the fluid
REFERENCES:
patent: 3082873 (1963-03-01), Bartelt
patent: 4176749 (1979-12-01), Wallace et al.
patent: 4265744 (1981-05-01), Weiffen
patent: 4342654 (1982-08-01), Lambert
Derwent Abstract Accession No. 84-242854/39, Class P41, SU, A, 1072-906 (Kazapoly), Feb. 15, 1984.
Bartelt, Dietrich, "Regulating Jig Discharge by Means of Radio-Isotopes", 4th Intl. Coal Preparation Congress, 1962, Papger B-2, pp. 89-97, (See pp. 94, 95-FIG. 7).
Wills, B. A., Mineral Processing Technology, "An Introduction to the Practical Aspects of Ore Treatment and Mineral Recovery", pp. 224-235, Pergamon Press, 1981.
Gaudin, A. M., Principles of Mineral Dressing, Chapter XII, pp. 250-259, McGraw-Hill Book Company, Inc., 1939.
Dept. of Chemical Engineering, Oregon State University, Chemical Reaction Engineering, Ch. 9, pp. 254-259, xix, John Wiley & Sons, 2nd Edition, 1972.
Hajec Donald T.
University of Queensland
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