Jigging
jigging
[′jig·iŋ]Jigging
a gravity-concentration method by which mixtures of minerals are sorted according to density in alternate upward and downward currents of water. The final products of jigging are tailings and concentrates of the desired minerals. Occasionally, an intermediate product is isolated that consists of concretions or mechanically produced mixtures of gangue particles and the desired mineral component.
In jigging, the sorting results from the periodic action of ascending and descending pulses of water on the bed of material being prepared, the jig bed, which rests on a jigging screen.
Figure 1 is a schematic representation of jigging. The pulsation causes the bed to alternately dilate and contract; as this takes place, particles with low density move to the upper layers of the bed, while those with high density are displaced to the lower layers. Each layer has its own characteristic density, and thus it is possible to separate the concentrate from the tailings and, in some cases, from the intermediate product.
The theory behind jigging was worked out by the German scientist P. Rittinger in 1867. Jigging technology was complicated by the principle of equal settling, which follows from Rittinger’s theory and which predicts that only a few narrow size-classes of particles will separate from the starting raw material. The subsequent work of the Hungarian scientist J. Fin-key (1924) and the Russian scientist P. V. Liashchenko (1935) on the settling of particles in a confined system demonstrated the feasibility of enriching dressing ores with a wider range of particle sizes.
A new theoretical treatment of jigging is based on the potential theory of jigging, which was advanced by the West German scientist F. Mayer in 1950. This theory analyzes the stratification of the entire jig bed, which tends toward a potential energy minimum, instead of analyzing the displacement of discrete particles. In the 1960’s the Soviet scientists N. N. Vinogradov and E. E. Rafales-Lamarka presented an analysis that treats jigging as a mass process that is affected by both random and strictly determined factors.
Jigging is used to dress minerals with a wide range of particle sizes—from 0.1 mm in alluvial ores to 250 mm in anthracites; the density of the jigged minerals can vary from 2,400 kg/m3, as in bituminous coals, to 15,000–19,000 kg/m3, as in gold and platinum. Jigging is sometimes the sole method of ore dressing in concentration plants, but in most cases it is combined with other methods, including preparation on concentration tables and sluices, magnetic separation, heavy-media separation, and flotation. It is one of the most economical methods in view of its high specific yield, low energy consumption, simplicity of the equipment used, and relatively high precision of separation— second only to the precision obtained with heavy-media separation. Jigging is a particularly suitable, economical method for extracting minerals in coarse inclusions, which do not require crushing to a small particle size, from coals and certain ferrous-metal ores. As of 1972, more than 40 percent of treated coal in the USSR was dressed by jigging.
REFERENCES
Samylin, N. A. Tekhnologiia obogashcheniia uglia gidravlicheskoi otsadkoi. Moscow, 1967.Spravochnik po obogashcheniiu rud, vol. 2. Moscow, 1972.
Coal Preparation, 3rd ed. Edited by J. W. Leonard and D. R. Mitchell. New York, 1968.
N. A. SAMYLIN