Influence of Dry Grinding by High-Pressure Grinding Rolls on Gold Recovery Efficiency During Cyanide Leaching

Traditional gold ore comminution circuits typically involve multi-stage crushing and grinding. However, conventional comminution processes can be energy-intensive and generate excessive fines, potentially reducing the efficiency of downstream hydrometallurgical processes. High-pressure grinding rolls (HPGR) technology promotes interparticle breakage through high-pressure compression between two counter-rotating rolls. HPGR treatment can induce microcrack formation within ore particles, potentially improving the accessibility of gold-bearing phases to cyanide solutions and enhancing gold extraction. To evaluate the effects of HPGR treatment on ore characteristics and subsequent gold extraction, two process-stream samples from the Raigorodok Gold Processing Plant (Akmola Region, Kazakhstan) were investigated: HPGR feed (1.405 g/t Au) and HPGR product (1.015 g/t Au). Particle-size distribution analysis indicated a reduction in the proportion of coarse particles and a redistribution of material toward intermediate size fractions following HPGR treatment, without a corresponding increase in excessive fines generation. Mineralogical analysis indicated no significant changes in the mineralogical composition of the ore following HPGR treatment. These findings suggest that the primary effect of HPGR treatment is related to particle-scale structural damage and microcrack formation rather than changes in mineralogical composition. Direct cyanidation and carbon-in-pulp (CIP) tests indicated improved gold extraction kinetics following HPGR treatment. The greatest improvement was observed during the first 2–6 h of leaching. Under comparable experimental conditions, gold extraction increased by 1–2% points. Overall, the findings suggest that HPGR treatment may improve subsequent cyanide leaching performance and support its integration into gold ore processing flowsheets.