Use of mineral liberation quantitative data to assess separation efficiency in mineral processing - Some case studies

Liberation assessment is a big challenge in mineral processing and its characterization is crucial to design the separation process. The development of automated image analysis methods allowed for the possibility of obtaining mineralogical data to quantify the liberation of the valuable minerals on a particle basis. The Mineral Distribution by liberation degree acquired by the QEMSCAN® system could be converted into Mass Distribution to obtain the Grade histogram (wt%). This Grade histogram (wt%) allows for the simulation of successive separations at different cut-off grades by accumulating the mass of each grade fraction to obtain the yield and the respective mineral recovery, conducting to the calculation of another upgrading line - the Ultimate Upgrading which could be graphically represented in a Mayer diagram along with the traditional Ideal Upgrading and No Upgrading lines. Ultimate Upgrading defines the technical limit of any separation process in accordance with the ore liberation degree. Subsequently, data of real separation (such as yield and metal recovery) can be graphically compared with the Ultimate Upgrading, assessing the separation performance; it is also possible to evaluate if better results would be obtained by re-adjusting parameters of the separator or if the degree of liberation should be increased. In the scope of the H2020 FAME project, this methodology was applied in two case studies, to evaluate the efficiency of gravity separation. Based on the results, the lack of liberation and the technical inefficiency of the separation were graphically identified on the Mayer diagram.