Mineral Processing

Factors That Affecting Shaking Table Gravity Separation

There are many factors affecting the work of the shaking table, among which the main stroke, the number of strokes, the concentration of ore feeding, the amount of ore feeding, the flushing water for the ore body, the lateral slope of the bed surface, and the nature of the ore feeding.

(1) Stroke and stroke times

The stroke and the number of strokes mainly affect the loosening, stratification and selective transportation of ore particles on the shaking bed. Stroke and stroke are two important factors that are related to each other. 

When selecting fine-grained materials, it is appropriate to use small strokes and high strokes, and when selecting coarse-grained materials, the opposite is true. For coarse-grained materials (2.0~0.074mm), the stroke can be adjusted between 15-27mm, and the stroke rate can be adjusted between 250-280 times/min. 

For slime, the stroke is 11-13 mm, and the stroke rate is 350-360 strokes/min. However, the most suitable stroke times are generally determined by experiments, and are generally not adjusted in operation.

(2) Flushing water and the lateral slope of the bed surface

The two mainly affect the movement speed of the ore particles in the lateral direction and the looseness of the foam layer. Increasing the slope can increase the speed of the water flow. Generally, when dealing with fine-grained materials, the slope should be smaller, and when dealing with coarse-grained materials, the slope should be larger. The slope can be adjusted in the range of 0°~10°. For the slope of different materials, the following values ​​can be used as a reference: 3.5°~4° for coarse-grained grades less than 2 mm; 2.5°~3.5° for materials less than 0.5 mm; less than 0.1 For fine-grained materials of millimeters, use 2°~2.5°; for slime (0.074 mm), use about 20 degrees.

It should be noted that the choice of slope should work well with the amount of water. The water flow is evenly distributed, without waves, the ore is not piled up, the selection zone is obvious, the width is thin, and the width of the non-mining area on the bed surface is appropriate.

The flushing water of the shaker consists of two parts: one part is the feed mineral water fed with the raw ore; the other part is the washing water directly fed to the bed surface. The transverse water flow needs to be adjusted properly. On the one hand, the bed should be loose enough to ensure that the light minerals in the uppermost layer can be washed away by the water flow. Therefore, the water layer on the bed surface must cover the bed. But on the other hand, it is necessary to ensure that the ore particles with high density can settle on the bed surface, so the lateral water speed and water volume should not be too large.

The amount of flushing water is related to the lateral slope of the bed surface, and within a certain range, “small water on a large slope” and “large water on a small slope” can obtain similar selection effects. When the slope increases, the amount of flushing water can be reduced, but the method of reducing the amount of flushing water and increasing the slope will narrow the mineral zones of different densities. When the quality of heavy minerals is required to be higher, a smaller slope is generally used to increase the flushing water. The flushing water and the bed slope are the factors that are often adjusted in the operation. When the two are adjusted properly, the water flow in the layered area will be evenly distributed on the bed surface, no waves, no ore piles, and obvious selection zones. The width is thin and the width of the non-mining area on the bed surface is suitable.

(3) Concentration of ore feeding, ore feeding amount and ore feeding body

The amount of dry ore and the concentration of ore fed to the shaker determine the volume of slurry fed. The ore feeding concentration and ore feeding volume have a great influence on the selection of the shaking table. If the ore feeding concentration is too large, the slurry is turned over and the fluidity is deteriorated, and many heavy minerals cannot be separated into layers; if the concentration is too thin, In addition to reducing the productivity of the shaker, fine concentrate is lost to tailings. The appropriate slurry concentration should ensure that the slurry has sufficient fluidity and the stratification and zonation of the ore particles on the bed surface. The normal feeding concentration of the shaker is generally 15%~30%.

 

The ore feeding volume is also an important factor in the operation of the shaking table. If the ore feeding volume is constant, the ore feeding concentration is too low and the pulp volume increases, which will cause the beneficiation recovery rate to decrease. If the amount of ore to be fed is certain, and the concentration of ore to be fed is too large, the recovery rate of beneficiation will also decrease. The amount of ore to be fed also depends on the particle size of the ore to be processed.

(4) Feeding properties

The density, particle size and shape of the medium ore particles have a great influence on the sorting index when the shaking table is used for ore feeding. When the density difference between heavy minerals and light minerals is greater than 1.5, it can be successfully sorted on a shaking table. Spherical-like ore particles and coarse particles are easily washed away by water. Shakers are generally used to classify materials, namely hydraulic classification. In the products obtained by hydraulic classification, the average particle size of heavy minerals is much smaller than that of light minerals, which is conducive to separation and stratification and improves separation efficiency.