Gold Heap Leaching Technology

After open-pit gold mining, resource recovery of low-grade ore or waste rock is crucial for improving the overall economic efficiency of the mine. Heap leaching technology, with its low production cost, high economic efficiency, relatively simple process, and rapid results, has become an ideal choice for processing such materials. The following will systematically describe the site setup, subgrade construction, and key auxiliary facilities for heap leaching.

I. Scientific Planning and Construction of Heap Leaching Sites

The site selection and construction of the heap leaching site are fundamental to the success of the process. The site should ideally be located between two ore bodies, approximately 200 meters from the mining area, to balance transportation costs and operational independence. A typical heap leaching system can be designed with six independently isolated heap leaching units, for example, four 58m × 52m and two 70m × 35m sites, with a total processing capacity of 100,000 to 140,000 tons of ore.

Site construction must adhere to strict standards: the base layer must be leveled with a bulldozer and compacted with a road roller to form a stable bearing surface. The site should be sloped according to a 300mm x 250mm grid, with a transverse slope of 5%-7% and a longitudinal slope of approximately 2% to ensure uniform flow and collection of the solution. To prevent debris from entering and reduce evaporation loss, the site should be equipped with a cover. Each heap leaching unit should be surrounded by a dike approximately 1 meter wide, with a minimum 5-meter gap between units to effectively prevent splashing of the sprayed solution and ensure operational safety.

II. Material Selection and Laying Process of the Impermeable Substrate

A reliable impermeable system is crucial for preventing the loss of precious solutions and protecting the environment. Currently, PVC (polyvinyl chloride) plastic sheets are commonly used as the substrate material due to their advantages: impact resistance, good ductility, excellent impermeability, and strong tear resistance.

During laying, the PVC sheets should be overlapped, with the overlap width controlled to approximately 200mm. A special adhesive (such as cyclohexanone) should be used for sealing and repairing any leaks. To enhance edge protection, the substrate at the edge of the ore heap needs to be widened. After laying, the substrate must be thoroughly rinsed with clean water. Next, a 150-200 mm thick layer of block ore is laid as a protective layer. This buffers the impact of subsequent ore loading, prevents damage to the base, and also facilitates uniform solution infiltration.

III. System Configuration of Key Auxiliary Facilities 

A complete heap leaching system relies on the following carefully designed auxiliary facilities, whose total volume must meet the requirements for at least 24 hours of solution circulation and maximum rainfall:

Solution Tank System: This mainly includes precious solution tanks, lean solution tanks, clear water tanks, spray tanks, and alkaline water tanks. Typically, two sizes of concrete tanks (e.g., 14m×26m×2m and 14m×12m×2m) are used, with a total volume of approximately 2773 cubic meters. The precious solution tanks and lean solution tanks are usually divided into several functional sub-tanks by concrete partitions, used for collecting gold-rich precious solutions, adsorption operations, precious solution purification, and preparing fresh spray solution, ensuring smooth flow and preventing cross-contamination of solutions.

Spraying and Adsorption System: The prepared spraying solution is pumped to a pipeline network laid on the ore heap for automatic or semi-automatic spraying. After collection, the precious solution is pumped to an adsorption column containing activated carbon for gold recovery. A control room allows for centralized control and monitoring of key processes such as spraying and adsorption.

Conclusion: Through the systematic site construction, rigorous seepage prevention measures, and supporting facility design described above, heap leaching gold extraction technology can safely, environmentally, and efficiently convert low-grade gold resources from open-pit mining into economic benefits. The successful implementation of this technology significantly extends the service life of mines and improves the comprehensive utilization level of resources.