ALTA 2014: Special aspects of continuous pressure oxidation of double refractory concentrates

ALTA 2014 5th Anuual Gold Event, Perth (Australia), 2014
Peter Zaytsev, Ilia Fomenko, Yakov Shneerson, Sergey Polezhaev, Mikhail Pleshkov

The Malomir ore is a double refractory material. The close association of gold with sulfide materials, as well as the presence of carbonaceous matter, impede gold recovery from such material to the cyanide solution. The sulfide carbonaceous concentrates of Malomir ore flotation will be processed at the Pokrovskiy POX hub. In this paper, we provide the results of POX technology testing at the batch (laboratory) and continuous (pilot plant) scale; in particular, the results of a kinetics study to define the optimal residence time under the oxidation conditions in the autoclave. Worldwide commercial and research practice shows that in some cases only the least refractory part of sulfide minerals can be oxidized in order to recover gold from refractory materials. However, the gold recovery from the Malomir concentrates increases throughout the entire oxidation process up to almost complete decomposition of sulfide sulfur. The negative effect of chloride ion and organic carbon impedes maximum gold recovery. This negative effect manifests itself at the end of the oxidation process, eliminates the gold recovery growth effect as the sulfides decompose and, finally, leads to a significant recovery reduction.

The results of the laboratory POX studies allow us to estimate the achievable level of gold recovery, as well as to note the general tendencies and relationships described above. The continuous process — due to its methodic features — is a more suitable tool for assessing the effect of different operating parameters on key process indicators at the end of the POX of double refractory materials. We use the pilot test results to evaluate in detail the effect of residence time and sulfide
sulfur oxidation on gold recovery. These results allowed us to introduce some meaningful changes to the design of the Pokrovskiy POX hub. We showed that it is possible — if needed — to increase the autoclaves’ throughput significantly. Otherwise, it is desirable to adjust the operating parameters in order to achieve the optimal gold recovery.