Sand gold beneficiation process

There are various types of placer gold deposits, which are widely distributed. Due to the free state of gold in placer gold and the significant difference in specific gravity with sand and gravel, the gravity separation process is an ideal and efficient method for extracting gold from placer ore.

The beneficiation process of gold placer mainly involves first recovering gold (with a recoverable gold particle size limit of generally 0.01mm) and its associated heavy minerals from the original ore as much as possible through the gravity separation process, and then separating gold and various heavy minerals through single or combined operations such as gravity separation, flotation, magnetic separation, and electrostatic separation, in order to achieve the goal of comprehensive recovery.

In the production process, the commonly used sand gold ore beneficiation process mainly includes ore washing operation, screening operation, re selection operation, and selection operation.

Mineral washing operation

The ore washing operation is an important process before the selection of placer gold mines. Its main purpose is to separate gravel, sand, and granular soil, and wash the fine mud adhered to the gravel from the mixed gold sand inside. Generally, placer gold often contains a large amount of weathered clay, and the gold sand is enclosed within it, forming cemented blocks or mud bodies together. If it is not crushed in advance, the agglomerates or mud will be discharged along with the waste rock during the screening process, thereby reducing the recovery rate of gold placer and causing gold loss.

In ore washing operations, first rinse with water and then use mechanical agitation such as a flat vibrating screen, cylindrical ore washing machine, and cylindrical screen to separate the mineral sand wrapped in cemented blocks or mud bodies, thereby separating gravel, sand, and clay, and washing away the clay and gold particles adhered to the gravel. This homework can improve the sorting ability of placer gold mines, which is beneficial for increasing the recovery rate of placer gold mines.

Screening operation

In general, the main purpose of screening operations is to screen the washed gold placer, remove large pieces of gravel that do not contain gold, and improve the efficiency of gold selection. In general, screening operations can remove 20-40% of waste rocks (gravel, pebbles).

The screening operation of gold placers often uses a water screen, which flushes water on top of the screen to crush and disperse the ore mud, in order to improve the screening efficiency of gold placers. Usually, the mesh size of the screening equipment for gold placers needs to be determined based on the particle size composition parameters of the gold in the original ore. Currently, the common mesh size is generally 10-20mm. When using a fixed chute for rough selection, the sieve hole can be larger, but the upper limit cannot exceed 60mm. Fixed selection plants often use vibrating screens or grid screens as screening equipment for gold placers, while gold mining ships often use cylindrical screens.

Gravity selection homework

The selection of placer gold mainly adopts the gravity separation process, firstly because the placer gold has a large specific gravity and coarse particle size, generally ranging from 0.074 to 2mm, and secondly because the gravity separation process is economical and simple. The re selection operation is a key task in the selection stage of placer gold mines, often using re selection equipment such as jigs, shakers, and chutes to discharge most of the waste rock and obtain coarse gold concentrate.

1.Jig machine：The selection of placer gold by the jigging machine can achieve a lower particle size of 0.04mm under the premise of a specific gravity difference of ≥ 1.25 and individual ore dissociation. The process operation is simple, the equipment processing capacity is large, and the application effect in rough selection of gold is very good.

2.Shaker：Shake bed gold beneficiation is suitable for processing minerals with finer particle sizes. Gold beneficiation is stable and reliable, with clear and visible distribution of ore belts. The rich ore ratio is higher than other beneficiation methods, making it easy to manage and capable of selecting the required ore in one go. According to the different particle sizes of ores, shakers can be divided into three types: coarse sand beds, fine sand beds, and mud beds. Coarse sand beds are suitable for sorting ore particles with particle sizes between 0.5 and 2.0mm; The fine sand bed is suitable for processing mineral particles with a particle size range of 0.074-0.5mm; Mud beds are suitable for processing mineral particles with a particle size of 0.037-0.074mm.

3.chute：

Coarse grained chutes are mainly used for sorting placer gold deposits, with an upper limit of feeding particle size of 100-200mm and an effective lower limit of recovering particle size of about 0.074mm. Fine grained chutes are commonly used for rough selection of coastal gold placers (with a gold particle size of -2mm).

The ore chute is suitable for sorting gold ore with a particle size of 2-0.074mm; The slurry chute is used to select -0.074mm sized gold deposits.

Selected assignments

According to different types of placer gold mines, selection operations can use gravity separation, magnetic separation, flotation, electrical separation, or combined processes to separate gold and various heavy minerals, in order to further improve the grade of gold. The selection operation is also an essential process in the beneficiation process of placer gold mines. Special attention should be paid to the selection of selection operation technology and equipment to avoid the loss of gold during the selection operation, fully improve the recovery efficiency of gold and other heavy sand minerals, and achieve the goal of comprehensive recovery.

Dehydration operation

We determine whether dehydration is necessary based on the process used in the selected assignment. The re selection, magnetic separation, and flotation processes can be carried out under wet conditions, while the electric separation process requires dry conditions. Generally, the dewatering operation of placer gold mines adopts a concentration+filtration process flow.

In actual production, the beneficiation process and equipment for gold placers need to be determined based on factors such as ore properties, plant conditions, and investment budgets. The same gold placer beneficiation process and equipment cannot be fully applicable to all gold placer beneficiation plants. Tailor a scientific and reasonable sand gold ore beneficiation process and equipment based on various factors.

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