Impact placer gold mainly refers to the gold formed by the separation of gold and quartz veins caused by river erosion in rock gold in mountains. Because this type of gold ore is as fine as sand, it is called placer gold. Since gold is in a free state in placer gold mines, and the difference in specific gravity between gold and sand is very obvious, gravity separation is an ideal method for extracting gold from placer mines.

The principle of the placer gold ore beneficiation process is to first use gravity separation to recover gold and various associated heavy minerals from the raw ore as much as possible. The lower limit of the particle size of gold that can be recovered by gravity separation is generally 0.01mm. In production practice, the placer gold ore beneficiation process generally includes crushing, screening, and gravity separation.

1. Impact placer gold ore crushing and screening operations
Many placer gold deposits contain cemented mud masses, some of which have a particle size greater than 100 mm, and sometimes are even cemented on gravel or pebbles. If not broken up in time, these mud balls will be discharged along with the waste rock during the screening process, resulting in the loss of gold.

The screening operation can remove 20-40% of waste rocks (gravel, pebbles) and is an indispensable operation in the placer gold beneficiation process. Among them, the screening parameters must be determined based on the particle size composition of gold in the raw ore sand. Depending on the washability of the ore, equipment such as a plane vibrating screen, a cylindrical screen, a scrubber with a screen, and a hydraulic washing bed can generally be used for screening operations.

2. Gravity and separation operations of impact placer gold ore
Due to the different particle size compositions of gold in placer gold mines, the effective particle size limits of materials processed by various gravity separation equipment are also different. Usually, placer gold ore beneficiation equipment mostly uses jig as placer gold ore roughing equipment, and shaking table as the beneficiation equipment for jig coarse concentrate; while some low-grade placer gold ore beneficiation uses chute as the beneficiation equipment. Rough selection equipment, jig as sweeping equipment, shaker as selection equipment. Therefore, a reasonable placer gold ore beneficiation process is mostly a joint operation of several gravity separation equipment.

① Jig selection
The main equipment of jig gold selection is the jig, which will mix mineral particles with different specific gravity and stratify them according to specific gravity in the vertically moving variable-speed medium flow. Minerals with small specific gravity are located in the upper layer, and minerals with large specific gravity are located in the lower layer. They can be reused. The stratified materials are discharged separately by the action of machinery and water flow.

The jig is suitable for sorting coarse mineral particles (mineral raw materials of any size except fine materials). The particle size range of metal minerals is 0.074-50mm. For placer gold ore dressing, it can be used when the specific gravity difference is ≥ 1.25 and the ore monomer is decomposed Under the premise of separation, the lower limit particle size can reach 0.04mm, the process operation is simple, the equipment processing capacity is large, and the application effect is very good in roughing gold ore.

② Shaker gold selection
The main equipment of the shaking table gold separation is the shaking table. It is a equipment for separation in the inclined medium flow. It uses the transmission mechanism to drive the bed surface to do longitudinal reciprocating motion, to perform flushing and differential motion of the bed surface, and the ore particles are reciprocating. It undergoes the stratification effect perpendicular to the bed surface and the separation effect parallel to the bed surface, so that materials of different particle sizes are discharged from different sections of the bed surface to achieve sorting.

Shaking table gold separation is suitable for processing and sorting minerals with finer particle sizes. It can be divided into three types according to the particle size of the ore: coarse sand bed, fine sand bed and mud bed. Among them, the coarse sand bed is suitable for sorting mineral particles with a particle size of 0.5-2.0mm, the fine sand bed is suitable for processing mineral particles with a particle size range of 0.074-0.5mm, and the slime bed is suitable for processing materials with a particle size of 0.037-0.074 mm of mineral particles.

The ore particle size range of shaking table gold separation is generally between 0.019-3mm. The gold separation is stable and reliable, the distribution of ore belts is clearly visible, the rich ore ratio is higher than other mineral processing methods, it is easy to manage, and the required ore can be selected at one time.

③ Chute gold selection
The gold separation chute is a device that uses inclined water flow for sorting. The material relies on the combined force of water flow, mineral gravity, friction between the mineral particles and the bottom of the chute, etc., to cause the ore particles to settle in different areas in the chute according to specific gravity. The material has a small specific gravity. The mineral particles are taken away by the water flow, leaving behind the mineral particles with a specific gravity, that is, the separation is completed.

In actual production, the placer gold ore beneficiation method and the configuration of placer gold ore beneficiation equipment need to be determined according to the specific ore properties and characteristics. Not all placer gold ore beneficiation plants can obtain the same ore beneficiation method and equipment. Ideal selection effect. It is recommended to conduct a mineral processing test first, and accordingly formulate a reasonable placer gold mineral processing method and tailor-made placer gold mineral processing equipment.