ALLUVIAL GOLD BENEFICIATION METHOD: IT'S NOT as DIFFICULT as YOU THINK
Asa Guo

Asa Guo

Mineral Processing Equipment PM. Node.js SE. Running Enthusiast. Ex-soldier of PLA.

ALLUVIAL GOLD BENEFICIATION METHOD: IT’S NOT as DIFFICULT as YOU THINK

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In the last article, we introduced ‘MINING of ALLUVIAL GOLD ORE DEPOSITS‘.
The topic I want to share with you today is ‘ALLUVIAL GOLD BENEFICIATION METHOD: IT’S NOT as DIFFICULT as YOU THINK’. In this article, I will introduce a beneficiation method for ALLUVIAL GOLD ORE.

alluvial gold wash plant case
alluvial gold wash plant case

Principle of gold ore beneficiation: first use gravity beneficiation method to recover gold and all kinds of associated heavy minerals from the original ore to the maximum extent. The gold and various heavy minerals are then separated from each other by a combination of gravity beneficiation, flotation, mercury mixing, magnetic and electrostatic separation. So as to achieve the purpose of comprehensive recovery. The beneficiation of alluvial gold ores is generally divided into fragmentation, screening, desliming and beneficiation.

1.Broken up and screen

Many alluvial gold deposits contain sticky mud clumps. Some of these clumps may have particle sizes greater than 100 mm. If these clumps are not broken up, the gold will be lost along with the waste rock during the screening process. In addition, the mud can cement on gravel or pebbles.

2.Desliming

Materials less than 0.1 mm in gold ore deposits generally contain little or no gold. Gold of less than 0.1 mm, commonly known as floating gold, is difficult to recover in mineral processing. However, the slime of the same grade will interfere the mineral processing process (especially the mechanical processing). Therefore, in the mechanical concentrator of gold ore, always try to remove the slime less than 0.1 mm. The commonly used desliming equipment in production is trommel screen. And sluice box allowed material granulation is relatively wide, and the handling capacity is large. Therefore, in many cases, no desliming is required before sluice box beneficiation.

3.Beneficiation

It has been proved by practice that gravity beneficiation is the most effective and economical method to treat gold ores. Due to the different particle size composition of gold in the ore gold deposit, the effective particle size limits of various gravity processing equipment are also different. Therefore, the reasonable process of alluvial gold ore beneficiation should be the joint operation of several gravity beneficiation equipment.

4.sluice box mineral processing technology

4.1 Introduction of sluice box

vibrating sluice box for placer gold
vibrating sluice box for placer gold

The method of ore beneficiation by means of water flowing in the sluice box is called sluice box beneficiation. It can handle materials with very different particle diameters. After the slurry is fed into the sluice box, the minerals with different specific gravity will be loosely stratified under the combined action of water flow force, gravity (or centrifugal force) of mineral particles, and friction between mineral particles and the bottom of the sluice box. At the bottom of the sluice box, the heavier material particles become concentrate, while the smaller ones are tailings.

The movement of mineral particles in the sluice box is very complex, and the main factors affecting the beneficiation effect of the sluice box are as follows:
①Stratification of upwelling flow
The motion of water flow in the sluice box is turbulent, which causes eddy currents and hydrojumps perpendicular to the bottom of the sluice box. This upwelling loosens the bed and helps to stratify mineral particles according to specific gravity.

②The separation function of inclined water
Driven by the inclined flow of the sluice box, the larger and more important mineral particles first settle to the place closer to the feeding point and become the bottom layer. The mineral particles with small particle size and specific gravity settle to the place far away from the feed point and become the topmost layer.

③Separation and stratification
Mineral particles that settle to the bottom of the trough continue to move along the bottom under the impetus of water flow. A fine mineral particle with a larger ratio in the upper layer will be transferred into the lower layer by gravity through the gap between the large mineral particles. This separation effect is weak in sluice box beneficiation.

④The action of friction
When mineral particles move in the sluice box, they are affected by the bottom of the sluice box and other mineral particles, which causes friction. The specific gravity and shape of mineral particles produce different frictional resistance, which results in different acceleration of mineral particles. This difference is beneficial to the sluice box mineral processing.

4.2 Technical parameters of sluice box

The slurry to solid ratio of the sluice box is 10:1, the slurry flow rate is 1-1.6m/s, and the slurry depth is about 20mm. The unit load of sluice box is 0.5-1.3 m/m.

The dip Angle of the sluice box is 5° ~ 7°(not exceeding 14° at most). The tank shall be placed directly on the gravel or soil according to the site conditions. Gravel entering the sluice box should be pre-screened to screen out boulders greater than 10 mm. sluice box made into three groups, two groups of work, one group clear, rotation work. You can also use only one group, intermittent operation. A set of sluice box is divided into two sections, each of which is 6 meters, and mortar flow is realized by overlapping between the sections. The 6-meter sluice box is also easy to adjust the slope. The first slope is slightly smaller than the second. The baffles on both sides of the sluice box are 30-50cm high. The daily treatment amount of the three sluice box with a length of 12 meters and a width of 0.9 meters is 1000-1200 cubic meters. Generally, the clearance time is 16-24 hours, and each time takes about 2 hours.

Plastic felt in foreign countries are generally used to spread the sports field, or decorate indoor and outdoor lawn, so also called artificial lawn. Plastic felt can be used in sluice box for gold selection. This kind of turf works well for gold selection. The bottom width of the sluice box is determined by the width of the gold-trapping felt. The width of the felt is generally used as the width of the sluice box. The general width of the felt sold in the market is 0.91-1 meters, a roll is 16 meters long. The shear felt length is 100-150cm, and the joints between the felt are connected by overlapped joints. It will be inconvenient to clear the felt if it is too long. The edges of the felt are pressed down with movable slats. Loosen the strip and roll the sand – bearing felt into a cylinder to remove. The gold – bearing sand obtained from the cleaning of felt is either shaken or washed by hand.

If you have any comments or suggestions, please feel free to leave a comment below or contact me directly.

This is the list of all articles in this series, welcome to read:

Workshop- Gongyi Forui Machinery Factory
Workshop- Gongyi Forui Machinery Factory

Gongyi Forui machinery factory, founded in 1986. We are one of the leading suppliers of beneficiation equipments in Asia. Don’t hesitate to Contact Us, if you have any question of beneficiation. And welcome to visit our company. Gongyi Forui Machinery Factory dedicated to serve you!

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