Laboratory and pilot plant studies on a cleaner spiral concentrator
circuit revealed that a chromite-rich stream cannot be discarded
prior to secondary ball milling of a UG-2 ore without
losing a significant amount of PGEs.
The laboratory and the pilot
plant runs showed that PGE losses of 16% and 14% respectively
would result when discarding the chromite-rich +106 lm fraction
of the cleaner heavies stream.
The data also indicated that the
PGMs were associated to some degree with the chromite minerals
in the UG-2 ore.
An alternative gravity and milling circuit configuration without
a Cr2O3 discard stream resulted in a significant improvement in the
PGE recovery (3.7%) and reduction in the Cr2O3 entrainment (32%).
This study confirms the benefit of the gravity and milling
circuit design for processing secondary UG-2 ore on industrial
concentrators.
An ore variability and plant economic study are
recommended.