Gravity separation is one of the commonly used methods for gold beneficiation. It uses different specific gravity of materials and different settling speeds in the medium to carry out stratified separation. Generally, in placer gold mines, gold mostly exists in the form of single natural gold, and its density difference with gangue is large.
There are various gravity separation methods, such as jig gravity separation, shaking bed gravity separation, chute gravity separation, spiral gravity separation, centrifugal gravity separation and wind gravity separation, etc. In gold ore dressing, the commonly used gravity separation methods are jig separation , shaking separation and chute separation.
The jigging process is to mix mineral particles of different specific gravity and stratify them according to their specific gravity in a vertical movement of variable speed media flow, with minerals of small specific gravity in the upper layer and minerals of large specific gravity in the lower layer, and then use the action of machinery and water flow to discharge the stratified materials separately.
Jigging is suitable for sorting coarse mineral particles (in addition to micro-fine materials of any size of mineral raw materials), the size range of its metal minerals beneficiation for 50mm-0.074mm, for alluvial gold beneficiation can be in the specific gravity difference ≥ 1.25 and the ore monomer dissociation premise, the lower limit of particle size up to 0.04mm, process operation is simple, equipment processing capacity is large, in the coarse gold ore in the use of good results.
The main equipment of shaking bed gold separation is shaking bed, it is in the horizontal medium flow in the selection of equipment, the use of drive mechanism to drive the bed to do longitudinal reciprocating motion, do impulse flow and bed differential motion, ore particles in the reciprocating motion of the bed perpendicular to the layering effect and parallel to the bed of the separation effect, so that different particle size of the material from the bed of different areas of discharge, to achieve separation.
Shaking bed gold processing suitable for processing sorting particle size of fine minerals, according to the different particle size of the ore, divided into coarse sand bed, fine sand bed and mud bed, which is suitable for sorting material particle size between 2.0mm-0.5mm, fine sand bed suitable for processing material particle size range of 0.5-0.074mm, mud bed suitable for processing material particle size of 0.074-0.037mm Ore particles.
The main equipment of the chute separation is the spiral chute, it is the use of inclined water flow for sorting equipment, the material with the water flow, mineral gravity, the friction between the particles and the bottom of the tank and other combined forces, so that the particles according to the specific gravity of the different zones in the tank, the specific gravity of small particles by the water flow away, leaving a large ratio of particles, that is, to complete the sorting.
The spiral chute is suitable for processing micro-fine materials with low mud content, with a particle size range of 0.6-0.03mm, simple structure, large throughput and low overall costs.
The above three gravity separation methods are only used for single dissociation of gold ore (alluvial gold ore), for vein gold minerals, rarely use the gravity separation process alone. Generally will be with other processes to form a joint process, such as gravity - flotation joint gold extraction process, gravity separation to assist gold extraction, in the grinding and classification circuit using jig, spiral chute and shaking bed with, first recovery of easy to dissociate the coarse particles of gold, for the subsequent flotation and cyanidation and other processes to create better separation conditions, can effectively improve the gold ore index and total gold recovery rate.
In gold ore beneficiation, the choice of gravity separation needs to be based on the nature of gold ore, it is recommended that the process selection is first carried out beneficiation tests, analysis of the nature of gold ore, through the test to determine whether it is suitable for the choice of gravity separation process, and to obtain the ideal gold separation process.
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