The content of gold in the ore is extremely low. In order to get high-grade gold, it is necessary to separate gold from the ore. However, the different types of gold ores lead to different separation methods. Gravity separation method is one of the commonly used methods for gold ore beneficiation, which uses different specific gravity of materials and different settling speed in medium to carry out stratified separation. Generally, in placer gold mines, gold mostly exists in the form of single natural gold and the density of placer gold is generally greater than 16t/m3, which has a large difference with the density of gangue. Therefore, the gravity separation process method for gold beneficiation is effective and economical.
There are many gravity separation methods in mineral processing, such as jigging gravity separation, shaking table gravity separation, chute gravity separation, spiral gravity separation, and centrifugal gravity separation. The commonly used gold gravity separation methods are jigging separation, shaking table separation, and spiral chute separation.
1. Jigging for gold separation
The main equipment for jigging gold separation is jigging machine. The jigging process is to mix mineral particles with different specific gravity. In the vertical movement of the variable-speed medium flow, the stratification is carried out according to the specific gravity. The minerals with a small specific gravity are located in the upper layer, and the minerals with a large specific gravity are located in the lower layer. The layered materials are discharged separately by the action of machinery and water flow.
Jigging gold separator is suitable for separating coarse mineral particles. For metal mineral processing, the grain size of the upper line is 50 mm and that of the lower line is 0.2-0.007mm. For placer gold beneficiation, the lower limit particle size can reach 0.04mm under the premise that the specific gravity difference is ≥1.25 and the ore monomer is dissociated. Jigging gold separation has the advantages of simple process operation, large processing capacity and the final product can be obtained in one selection.
2. Shaking Table for gold separation
The main equipment for selecting gold in the shaker is the shaking table. It is a device for separation in a horizontal medium flow. The transmission mechanism is used to drive the bed surface to make a longitudinal reciprocating motion, at the same time, the impact flow and the bed surface difference are used to make the movement. In the reciprocating movement, the ore particles are subjected to the stratification action perpendicular to the bed surface and the separation action parallel to the bed surface, so that the materials with different particle sizes are discharged from different sections of the bed surface to realize separation.
Shaking table for gold beneficiation is suitable for processing and sorting minerals with finer particle size. It can be divided into three types: coarse sand bed, fine sand bed, and slime bed according to the different particle sizes of the ore. Generally, the feed particle size range of the shaker gold separation machine is 3 ~ 0.019mm. The advantages are stable and reliable operation, clear distribution of ore belt, higher rich ore ratio than other beneficiation methods, easy management, and one-time separation of required ores.
3. Chute for gold separation
The main equipment of chute for gold separation plant is spiral chute, which uses inclined water flow for separation. With the combined force of water flow, mineral gravity and mineral particles, and the friction force seen at the bottom of the tank, the materials make the mineral particles settle in different areas in the tank according to their specific gravity. The mineral particles with a small specific gravity are taken away by the water flow, and the ore particles with a larger proportion will be left behind, which means the separation is completed. The spiral chute is an intermittent operation. When the concentrate at the bottom of the chute settles to the moving degree, it is necessary to stop feeding and remove the concentrate before the operation. The spiral chute is suitable for processing fine-grained materials with low mud content with material size ranges from 0.6 to 0.03mm. Spiral chute for gold beneficiation has the advantages of simple structure, large processing capacity and low comprehensive cost.
The above three methods of
gold gravity separation are only used for gold mines with monomer dissociation (placer gold mines). For vein gold minerals, the gravity separation plant is rarely used alone, it is generally combined with other processes to form a combined process, such as combined gravity extraction and flotation process. Gravity separation equipment is used to assist gold extraction. The jig, spiral chute, and shaker are used in the grinding and grading circuit to first recover the easily dissociated coarse particles of gold to create better results for subsequent flotation and cyanidation processes, which can ultimately effectively improve the gold mine index and the total gold recovery rate.
