Abstract

Dry processing of metal containing ores is often easily discarded as a viable option because of the higher energy consumption of dry grinding and several other challenges introduced from the handling of the dry ore. However, possible positive aspects include improved surface properties, reduced wear of the grinding media, and improved efficiency of water usage, which will become increasingly important in the future due to the water scarcity and global warming.

Laboratory scale flotation tests with various grinding and conditioning methods were conducted with the Pyhäsalmi massive sulphide ore (Cu-Zn) and the Syväjärvi spodumene pegmatite silicate ore (Li) to determine the effects of dry processing on the flotation performance of these ores. Products were characterized utilizing XRF and MP-AES, and metallurgical efficiency was assessed. EDTA-leaching of the grinding products, and electrochemical measurements were conducted to further assess the chemical conditions after various processing atmospheres.

Dry grinding the Pyhäsalmi sulphide ore resulted in higher flotation mass recoveries compared to wet grinding, but at the cost of selectivity. Beneficial effects emerging from the chemical conditioning during grinding were observed regarding kinetics, selectivity, and overall performance. Conditioning the Syväjärvi spodumene ore with a fatty acid collector during dry grinding had a tremendous activating effect on the ore, and detrimental effect on the selectivity. Overall, the spodumene ore responded poorly to the dry processing conditions, but some potential applications were identified.

These initial results showed clear differences in the separation performance between the various grinding and conditioning conditions, and future efforts will be focused on determining the effects of these different processing conditions on the mineralś surface properties in a more precise manner.