Gravity beneficiation is one of the commonly used methods for gold beneficiation. It mainly uses the different specific gravity of the material and the different settling speed in the medium to carry out the stratified separation. In placer gold mines, gold mostly exists in the form of single natural gold, which has a large difference in density with gangue. The gravity beneficiation method is both effective and economical.
There are many kinds of gravity beneficiation methods, such as mineral jig gravity beneficiation, shaker gravity beneficiation, sluice box gravity beneficiation, centrifuge gravity beneficiation and wind gravity beneficiation. In gold ore beneficiation, the common gravity beneficiation methods mainly include three methods: jigging, shaking table, and sluice box.
1. JIGGING GOLD BENEFICIATION PROCESS
The jigging equipment is mainly a jigging machine. The jigging process is to mix mineral particles with different specific gravities and stratify according to specific gravity in a vertically moving variable-speed medium flow. Minerals with low specific gravity are located in the upper layer, and minerals with high specific gravity are located in the lower layer. Then use the action of machinery and water flow to discharge the layered materials separately.
Scope of application: jigging gold is suitable for sorting coarse mineral particles (mineral materials of any particle size except fine materials). For metal mineral beneficiation, the upper limit of the particle size is 50mm, and the lower limit is 0.2-0.007mm. For placer gold beneficiation, under the premise that the specific gravity difference is ≥1.25 and the ore monomer is dissociated, the lower limit particle size can reach 0.04mm
Advantages: simple process operation and large equipment processing capacity. The final product can be obtained in one selection.
2. SHAKER GOLD BENEFICIATION PROCESS
The main equipment for selecting gold in the shaker is the shaker. It is a device for selection in a horizontal medium flow. It utilizes a transmission mechanism to drive the bed surface to make longitudinal reciprocating motion, and make the rush and bed surface differential motion. The ore particles undergo stratification perpendicular to the bed surface and separation effect parallel to the bed surface in the reciprocating motion. The materials of different particle sizes are discharged from different sections of the bed surface to realize sorting.
Scope of application: Shaker gold selection is suitable for processing minerals with finer particle size. According to the different particle size of the ore, it can be divided into three types: coarse sand bed, fine sand bed and ore mud bed. Among them, the coarse sand bed is suitable for sorting ore particles with a material particle size less than 0.5mm. The fine sand bed is suitable for processing ore particles with a particle size of 0.5～0.074mm. The sludge bed is suitable for processing ore particles with a material size of 0.074～0.037mm.
Advantages: The feed size range of shaker gold selection is generally between 3~0.019mm. The gold selection is stable and reliable, and the distribution of the ore belt is clearly visible. The recovery rate is higher than other beneficiation methods, easy to manage, and the required ore can be separated at one time.
3. THE SLUICE BOX GOLD BENEFICIATION PROCESS
The main equipment for selecting gold in the sluice box is a drum screen and a sluice box. It is a sorting device using inclined water flow. Under the combined force of water flow, mineral gravity, and friction between the mineral particles and the bottom of the tank, the materials make the mineral particles settle in different zones in the tank according to their specific gravity. The ore particles with a small specific gravity are taken away by the water flow, leaving behind the ore particles with a high specific gravity, and the sorting is completed. The sluice box requires intermittent operation. When the concentrate at the bottom of the sluice box is deposited to a certain extent, it is necessary to stop feeding the ore and take out the concentrate. Then continue the beneficiation operation.
Scope of application: The sluice box gold selection method is suitable for processing fine-grained materials with low mud content, and the particle size range of the material is 0.6~0.03mm.
Advantages: simple structure, large processing capacity and low overall cost.
The above three methods of gravity beneficiation and gold beneficiation are only used for gold ore with monomer dissociation (placer gold ore). For vein gold minerals, the gravity beneficiation process is rarely used alone, and it is generally combined with other processes to form a combined process. For example, the combined process of gravity beneficiation and buoyancy beneficiation. Gravity beneficiation plays the role of auxiliary gold selection. In the grinding and classification process, using equipment such as jigger, sluice box and shaker, first recover the easily dissociated coarse particles of gold to create better separation conditions for subsequent flotation and cyanidation processes. In the end, it can effectively improve the gold mine index and the total gold recovery rate.
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