Equipment and workflow for extracting placer gold
published date: 10-12-2020
The beneficiation principle of placer gold ore is to first use gravity separation to maximize the recovery of gold and its associated heavy minerals from the original ore sand, and then use the combined work of gravity separation, flotation, amalgamation, magnetic separation, and electrostatic separation. Gold and various heavy minerals are separated from each other to achieve the purpose of comprehensive recovery. The sorting of placer gold ore is generally divided into the processes of disintegration and screening, desliming and sorting.
Disintegration and screening
Many placer gold mines contain cemented sludge, some of which have a particle size greater than 100 mm. If this sludge is not disintegrated, it will be removed with the waste rock during the screening process, causing gold loss. In addition, the mortar can be cemented on gravel or pebbles. If it is not broken, it will also cause gold loss during the screening process. On the gold dredger, crushing and screening are done in a cylindrical screen (trommel screen). When operating, the washing water pressure in the cylindrical screen should not be less than 35 kPa.
Screening operation can remove 20-40% of waste rock (gravel, pebbles), which is an indispensable part of placer gold beneficiation. The determination of reasonable screening parameters must be based on the measurement data of the particle size composition of the gold in the original ore. At present, the sieve openings selected in placer gold mines are generally 10-20 mm. For example, when a fixed chute is used as a roughing equipment, the sieve openings can be larger, but cannot exceed 60 mm.
The commonly used desliming equipment is desliming bucket or spiral chute, the latter with large processing capacity.
Practice has proved that the reselection method is an effective and economical method for dealing with placer gold mines. Because of the different particle size composition of gold in placer gold mines, a reasonable placer gold ore beneficiation process should be a joint work of several gravity separation equipment.
The gold-bearing concentrate obtained from the rough selection section has a gold grade of 100 g/ton, and heavy sand minerals are mostly above 1 to 2 kg/ton. There are currently three methods for processing gold-bearing crude concentrate: 1. After the gold particles are discharged, the heavy sand is discarded; 2. The amalgamation cylinder is used for internal amalgamation, and the amalgam is obtained and the heavy sand is discarded; 3. After the gold is extracted by manual elutriation or amalgamation, the minerals are sent to the concentration plant for processing and magnetic separation , Electrical separation and other methods to recover various minerals.
The gold recovery rate of the placer gold mine: the two-stage chute separation is 70-74%, and the chute rough selection, jig sweeping and shaking table selection processes are 75-80%.