Upscaling of RoStar® Ultrafine Grinding Mill – Geometallurgical follow-up

Abstract

Decreasing high ore grade deposits have exposed the need of processing more and more low grade, complex, not fully liberated and finely disseminated ores or even “urban mine” wastes, moreover combined with increasing comminution inefficiency in reducing particle size of conventional tumbling mills, have delivered the necessity to find distinct process or technology ensuring full liberation of minerals of interest. A new technology has been gaining popularity widely accepted in the last few decades, resulting in superior energy utilization and efficiency. The technology is known as stirrer mills, which are widely used for fine and ultrafine grinding (Gupta and Yan 2016).

The present study is emphasized on the influence and the effect ultrafine grinding obtained from regrinding with RoStarMill® upon downstream processes, such as flotation. Further evaluation and modelling of bulk concentrate flotation performance in order to find out, understand and provide guidelines for floating ultrafine particles at Assarel beneficiation plant is targeted.

Mineralogical characterization (Optical microscopy and SEM-ZEISS MINERALOGIC) and granulometry studies have been available for the bulk concentrate and RoStar output at 1 and 3 minutes. In order to replicate RoStar mill output (particle size distribution) a Magotteaux Mill® was implemented during the research work. All comminution and flotation experiments have been executed at the Research Laboratory of Mineral Processing in University of Liege in batch mode by using Magotteaux Mill® and Magottaux float cell™. The effect of specific energy input on Magotteaux mill performance was monitored and recorded, but it cannot be compared with RoStarMill®, prototype and pilot RoStarMill® are situated in TU Bergakademie Freiberg.

In this study, flotation response was investigated by changing variety of parameters such as regrinding time, reagent consumption, and hydrodynamic conditions in the cell. Additionally, flotation trials were carried out separately with initial classification and separation of flotation feed to distinguish fine and ultrafine particle size classes via lab scale hydrocyclone (cut size 20 µm).

Flotation response in terms of recovery are in the range of 75.1 to 84.5 % indicating that ultrafine particles float relatively easy at certain conditions, such as increased agitation and flotation time, intensive mixing, higher turbulence conditions in the cell and required dosage of collector (xanthate), but may lead to raising of collector addition. Moreover, regrinding with RoStar Mill shows improved liberation of chalcopyrite to 31.9 % after 1 min and 42.1 % after 3 min of regrinding respectively.

Further test work is suggested to be carried out at Assarel mine site, after delivering containerized pilot plant of MMS RoStar to proceed with investigation of flotation response directly from RoStar output.