Gold tank leaching is a method of extracting gold from gold ore, mainly used to process low-grade gold-containing ores. The following is a general process flow of gold tank leaching:

1. Ore preparation First

The mined gold ore needs to be crushed and ground to increase the surface area of the ore and improve the leaching rate of gold. The particle size of the crushed ore is usually 30-50mm, or even finer to 9-19mm.

2. Leaching pad construction

Before tank leaching, a leaching pad needs to be built to prevent solution leakage. The material of the leaching pad can be clay, sand, gravel, asphalt, reinforced concrete, plastic film or rubber plastic sheet. The thickness of the pad is generally 300-600mm. The longitudinal and transverse drainage ditches are paved on the pad with lump ore, and finally a layer of large ore is laid on the entire bottom plate to protect the bottom pad.

3. Pile up

The crushed ore is transported to the leaching pad, and the ore is piled into a certain height using pile-building machinery such as trucks and bulldozers. The height of the ore pile is usually 3-9m, and the original ore heap leaching pile can be as high as 46m. There are multiple pile methods, multi-layer method, slope method, etc.

4. Preparation of leaching solution

The solution for leaching gold is prepared, and sodium cyanide solution is usually used as the leaching solution. The formula and dosage of the leaching solution need to be determined according to the type of ore, mineral composition and chemical composition.

5. Liquid distribution and liquid collection 

The leaching solution is evenly sprayed on the top surface of the ore pile, and the liquid distribution system is composed of a liquid distribution tank, a pump, a liquid infusion pipe, and a spray pipe and a sprinkler laid on the ore pile. The spraying intensity is usually 0.1-0.4L/m·min, and the spraying time accounts for about 1/3-1/2 of the total time. After spraying, the rich liquid from the bottom of the pile is collected into the liquid collection tank through the liquid ditch, and then pumped to the workshop for processing.

6. Rich liquid processing

The leaching solution is treated with activated carbon adsorption or zinc powder replacement to separate gold from the solution. Activated carbon becomes gold-carrying carbon because it adsorbs gold in the ore pulp. After the adsorption operation is completed, the ore pulp containing gold-loaded carbon is sent to the carbon screen through an air lift to separate the ore pulp from the activated carbon. After screening and washing, the ore pulp is sent to the desorption electrolysis operation. Under high temperature and high pressure conditions, anions that are easily adsorbed by activated carbon are added to the desorption system to replace Au(CN)2- to obtain gold mud and lean carbon, thereby achieving gold desorption. The precious liquid obtained by desorbing the gold-loaded carbon is recovered by ionization to obtain solid gold.

The above is the general process flow of gold mine tank leaching, and the specific process steps should also be determined according to the actual ore characteristics. In the actual production process, different gold ore properties are suitable for different tank leaching process flows and parameters, which need to be determined through sufficient mineral processing tests.