Investigating the benefits of using HPGR prior to cyanidation of low grade gold ore

It is known that the cracked structure of the particles has positive effects in leaching processes. In this respect, high pressure grinding rolls (HPGR) provides some advantages such as increasing leaching efficiency and reducing leaching time by creating more cracked particles compared to other crushers. Although there are studies on the advantages of HPGR on different ores, these have not been fully demonstrated in low grade gold ores, and leaching kinetics have not been examined in detail in the studies conducted in this context. In this study, first of all, crack formation in a low grade gold ore by crushing with HPGR and jaw crusher was investigated. Then, bottle roll tests were performed in different size fractions and different cyanide concentrations along with column leaching of the pelletized ore in a single test condition. As a result of the studies, it was determined that 2–3 times more cracked particles were formed in HPGR depending on the particle size. It was shown that the modified Kelsall model explains the kinetics better than other kinetic models tested. In summary, it was revealed that maximum gold extractions are almost same for HPGR and jaw crushers. However, the fast dissolution kinetic constant was found to be around 25% higher for HPGR than for the jaw crusher in bottle roll tests while this ratio was approximately 30% higher in column leaching tests, suggesting a distinct influence of the crushing method on the dissolution kinetics.