[Introduction]: Heap leaching (HL) is a flexible and economic gold ore processing method used to extract gold from low-grade gold ores. In this process, the ore is firstly crushed to fine particles. By spraying the leaching solution to the large piles, the gold-containing solution is leached. Then used the gold processing method of carbon adsorption, zinc powder displacement device, and so on to separate gold from the liquid.
[Application]: Heap leaching process is always used for low-grade ore, small gold mines, or both. These ores can not be processed by using the conventional gold ore processing method.
Gold heap leaching process means to transfer the raw ore to the prepared yard, or directly stock on the waste rock or low-grade ore, then use cyanide leaching liquid to spray or infiltrate, and the ore reacts with the cyanide leaching liquid. After several recycling of leaching liquid and repeat spray, the leaching liquid can be collected. Then, treating leaching liquid by the activated carbon or metal zinc method and the barren solution returns to heap leaching operation for reuse.
The raw ore is crushed into fine particles (30-50mm) by using jaw crusher or cone crusher, then will be heap leaching directly; or pelletization (fine particles are pelletized into bigger lumps ), then piled by forklift.
Generally, the heap leaching site is the gentle slope hills (natural grade 5-15 ˚) that nears the mining site. Removing weed sand lose material firstly, and then consolidate it as the foundation with 5 ˚gradient. The sides are high and the middle is low, which makes leach liquid flow into the stationary tank easily. The yard is covered with a geomembrane to prevent leakage. Around the storage yard, a 0.4-meter ridge of soil shall be built as a ditch to prevent the rainwater from flowing into the yard. Besides, build a 0.3-meter-thick of lean ore before stacking the ore.
Then the large piles will be sprayed by the leaching solutions, through which the gold-containing solution will be leached from the piles. The pregnant liquid will flow into pregnant solution pool. Then used the gold ore processing method of adsorption of activated carbon, zinc powder displacement device and so on to separate gold from the liquid. The tail liquid will be recycled.
The gold heap leaching process has a low production cost and can be put into production quickly. In addition, the scale of heap leaching is more flexible, even more than tens of thousands of tons. Heap leaching or granulated heap leaching can be adopted after the ore is crushed to a certain size.
