cases
The ore type included gold oxidized ore and sulphide ore. The average grade of Au in the oxidized ore was 2.5g/t; The average grade of Au in the suphide ore was 3.39g/t, the average grade of Ag was 40.75g/t.
Crushing & Screening: the crushing and screening system adopts a two-and-a-half-stage crushing process with one closed circuit. ROM ore is fed through a jaw crusher for primary crushing, followed by secondary and fine crushing, with closed-circuit screening to ensure particle size control. The final crushed product size is –15 mm.
Grinding & Classification: the grinding and classification system uses a two-stage closed grinding circuit for oxidized ore, achieving a fineness of 85–90% passing –200 mesh. A reserved ball mill system is planned for future sulphide ore treatment, targeting 90% passing –325 mesh. Hydrocyclones are used to form closed-loop classification and regrinding.
Alkali Pretreatment: the alkali pretreatment system thickens the hydrocyclone overflow and treats the slurry in double-impeller leaching tanks. The alkali pretreatment duration is 24 hours to condition the slurry before cyanidation.
Leaching & Two-Stage Washing: the leaching and washing system conducts cyanide leaching in double-impeller tanks. The leaching time is 32 hours for oxidized ore and 24 hours for sulphide ore. This is followed by two-stage washing using high-efficiency thickeners to recover pregnant solution, while the final underflow proceeds to the tailings dry stacking system.
Zinc Powder Replacement: the zinc powder replacement system purifies and deoxygenates the pregnant solution before zinc addition. Removing dissolved oxygen reduces zinc consumption and prevents gold and silver re-dissolution. Gold and silver mud is recovered through filtration and smelted into bullion, while barren solution is recycled back to the process.
Tailings Dry Stacking: the tailings dry stacking system adopts filter pressing combined with tailings rewashing. Chemicals are added to remove harmful ions prior to filtration. After dewatering, the final tailings moisture content is controlled at ≤18%, meeting environmental requirements for dry stacking.
Finally, the purity of gold was higher than 99.5%, the purity of silver ingot was higher than 99.5%.
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