What is the process of placer mining?

There are many kinds of placer gold deposits and they are widely distributed. Because gold is free in placer gold and the specific gravity difference between gold and sand is very obvious, What is the process of placer mining?

The gravity separation process is an ideal and efficient method to extract gold from placer gold.

砂金1 1 - What is the process of placer mining?

The beneficiation process of mining placer gold ore is mainly to recover gold (the lower limit of the recoverable gold particle size is generally 0.01mm) and its associated gravity minerals from the raw ore as much as possible through the gravity separation process, and then go through a single method such as gravity separation, flotation separation, magnetic separation and electrostatic separation. Or combined operations to separate gold and various heavy sand minerals, so as to achieve the purpose of comprehensive recovery.

In the production process, the commonly used placer gold ore beneficiation process mainly includes washing operations, screening operations, gravity operations and concentration operations.

1. Washing operation

Ore washing operation is an important process before the separation of the placer gold mine. Its main purpose is to separate gravel, sand, and grained soil, and wash the fine mud adhered to the gravel and the mixed gold ore sand. Generally, placer gold often contains more weathered clay, and gold sand is wrapped in it, forming cemented block or slurry.

If it is not broken in advance, the cemented block or slurry will be discharged along with the waste rock in the screening process, thereby reducing the recovery rate of the placer gold and causing the loss of gold.

In the ore washing operation, the raw ore sand wrapped in the cemented block or slurry body is dissociated by washing with water and then mechanically stirred by a plane vibrating screen, cylindrical scrubber, cylindrical screen, etc., thereby separating gravel, sand, and clay. , Wash the clay and gold particles adhered to the gravel. This operation can improve the separation ability of placer gold and is beneficial to improving the recovery rate of placer gold.

2. Screening operation

Under normal circumstances, the main purpose of the screening operation is to screen the washing placer gold ore, to screen out large pieces of gravel that do not contain gold, to improve the efficiency of gold separation. Generally, the screening operation can screen out 20-40% of the waste rock (gravel, pebbles).

The screening operation of placer gold ore mostly adopts a water screen and flushes water on the screen to break up the ore slime, to improve the screening efficiency of placer gold ore. Generally, the screen hole size of placer gold screening equipment shall be determined according to the particle size composition parameters of gold in raw ore. at present, the common screen hole is generally 10-20mm. When the fixed chute is used for roughing, the screen hole can be larger, but the upper limit cannot exceed 60mm. Placer gold concentrators often use vibrating screens or grid screens as the screening equipment for placer gold ore, while small placer gold mining often uses mobile gold washing plant.

3. Gravity operation

The separation of placer gold ore mainly adopts the gravity separation process of mining. One is the specific gravity and coarse grain size of placer gold are generally 0.074~2mm, and the other is the gravity separation process is economical and simple. Gravity separation is a key operation in the beneficiation stage of placer gold mines. Gravity separation equipment such as jig machines, shaking table, and chutes are often used to discharge most of the waste rocks to obtain crude gold concentrate.

The jig machine can separate the placer gold under the premise that the specific gravity difference is ≥1.25 and the ore monomer dissociation, the lower limit particle size can reach 0.04mm, the process operation is simple, the equipment processing capacity is large, It has a good application effect in roughing gold mine.

Shaking table gold separation is suitable for processing and separating fine-grained minerals. The gold beneficiation is stable and reliable, the ore belt distribution is clearly visible, the rich ore ratio is higher than other beneficiation methods, easy to manage, and can be used to separate the required ores at one time.

According to the different particle sizes of the ore, the shaking table can be divided into three types: coarse sand bed, fine sand bed and ore mud bed:

◆   The coarse sand bed is suitable for sorting ore particles with material particle size between 0.5-2.0mm;

◆   The fine sand bed is suitable for processing ore particles with a particle size range of 0.074-0.5mm;

◆   The ore slime bed is suitable for processing ore particles with a material particle size of 0.037-0.074mm.

According to the particle size of sorted ore particles, the chute can be divided into the coarse-grained chute and fine-grained chute. Among them, the fine-grained chute can be divided into ore chute and ore slime chute.

◆ The coarse-grained chute is mainly used for sorting placer gold ore. The upper limit of the feeding particle size can reach 100-200mm, and the lower limit of the effective recovery particle size is about 0.074mm.

◆ The fine-grain chute is often used for roughing operations of sorting seashore placer gold mines (gold mine particle size is -2mm);

◆ The ore chute is suitable for sorting 2-0.074mm grain size gold ore;

◆ The ore slime chute is used to sort -0.074mm grain size gold ore。


4. Selection operation

According to different types of placer gold ore, the concentrating operation can be carried out by gravity separation process, magnetic separation process, flotation process, electric separation process or combined process. Separate gold and various heavy minerals from each other to further enhance the gold grade. The beneficiation operation is also one of the indispensable procedures in the beneficiation process of the placer gold mine. Special attention should be paid to the selection of the selection process and equipment to avoid the loss of gold during the selection process and fully improve the gold and other heavy sand minerals. Recycling efficiency, to achieve the purpose of comprehensive recycling.


5. Dehydration operation

Usually, we judge whether the dehydration operation is necessary according to the process used in the concentrating operation. Gravity separation, magnetic separation, and flotation processes can be carried out under wet conditions, while electrical separation processes require dry conditions. Generally, the dehydration operation of the placer gold mine adopts the concentration + filtration process.

In actual production, the beneficiation process and beneficiation equipment of the placer gold ore need to be determined by combining the nature of the ore, the condition of the concentrator, and the investment budget. The same process flow and beneficiation equipment of the placer gold ore are not completely suitable for all placer gold ore beneficiation. factory. Therefore, it’s recommended to select equipment manufacturers with beneficiation qualifications, combining various factors to tailor a scientific and reasonable placer gold beneficiation process and equipment.

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In actual production, the beneficiation process of mining and equipment of placer gold ore need to be determined in combination with ore properties, concentrator conditions, investment budget and other factors. The same placer gold ore beneficiation process and equipment can not be fully applicable to all placer gold ore concentrators. Therefore, it is recommended to select equipment manufacturers with beneficiation qualifications and customize scientific and reasonable placer gold beneficiation process and equipment in combination with various factors.

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