The liberation effect of magnetite fine ground by vertical stirred mill and ball mill

Abstract

A magnetite middling was used to compare the liberation effect of the magnetite fine ground by a vertical stirred mill and a ball mill. The magnetite middling contained a high content of magnetite intergrowth with the particle size mainly distributed in the range of 40–150μm. The new generated −38μm products were concentrated by magnetic separation. Particle size distribution, the degree of mineral liberation and section micrograph of new generated −38μm products were measured by laser particle size analyzer, mineral liberation analyzer (MLA) and scanning electron microscope respectively. It was found that stirred milling improved the degree of liberation of magnetite selectively. The degree of liberation of magnetite in new generated −38μm product of stirred milling is 8.1% points higher than that of ball milling and stirred milling mainly improved the degree of liberation of magnetite in +10 to −38μm size fractions. In the size fractions with identical P80, the degree of liberation of the magnetites in the products of stirred milling is greater than that of ball milling, with the value varied from 2.4% to 29.1% points. The iron grade of magnetic separation concentrate of stirred milling is 5.2% points higher than that of ball milling. The average particle size of new generated −38μm products by stirred milling is finer when comparing with that by ball milling. The stirred mill was fit to use for fine grinding the middling with a high content of complex intergrowth, especially appropriated for milling P80 10–30μm minerals to liberate more valuable metals.