Abstract
The Bureau of Mines conducted magnetic belt cobbing field-scale research with the Inland Steel Mining Company and the Minnesota Department of Natural Resources. Sixty-seven field tests were conducted on three iron ore types, ranging from 10 to 24 pct magnetic iron, and at two different ore sizes, namely the secondary crusher discharge (3 x 0 inches) and Tertiary crusher discharge (1 x 0 inch). Field cobbing of the test materials produced an enriched iron ore concentrate and a low-grade reject material. Successful ore separation and enrichment occurred with both Tertiary and secondary crusher feed stocks. Certain material types currently considered to be uneconomic were upgraded using the dry magnetic cobbing process to produce a millable ore concentrate. Best magnetic iron recoveries after cobbing ranged from approximately 78 to 95 pct for the Tertiary feed and 50 to 95 pct for the secondary crusher feed. The tests indicate that the lean-grade ore types (lc2 and lc5) lend themselves to dry magnetic cobbing, producing an enriched concentrate with noticeable upgrading. Additionally, the coarser size of those lean ore types produced the higher grade magnetic iron. Additional testing under more optimum operating conditions is warranted to prove out the validity of incorporating dry cobbing technology into mining of lean-grade taconite ore.
