Recuperação de sulfetos em minério de zinco predominantemente silicatado

Abstract

Studies developed at Vazantes mine indicated the presence of zinc, copper, lead, and silver sulfides, suggesting the search for alternatives to recover these minerals. Considering that the silicate zinc concentrate is the main product, the concern was not to alter the zinc silicate flotation parameters. Due to the fact that the liberation size between the zinc and lead sulfide minerals is 16 m and the size distribution of the silicate flotation feed is 18% retained in 150 m, the first stage of the pilot scale testwork consisted of bulk flotation aiming at the separation of the sulfides from the other minerals preventing the production of fines that would impair the silicate zinc flotation. The bulk concentrate was then reground to reach the liberation degree required for the separation between lead and zinc sulfides. In the industrial process the bulk flotation tailings will follow to the zinc silicate flotation without any change in size. The pilot scale tests yielded lead silver concentrates presenting average weight recovery of 39%, average grades of 62% Pb and 4815 ppm Ag, at metallurgical recovery levels of 44.9% and 66.8%, respectively. The sulfide zinc concentrate reached average weight recovery of 14% and average zinc grade of 49%. The start up of the industrial plant faced a variable that was not previously studied, the change in lead and silver grades in the feed. The ROM feeding Vazantes concentrator presented lead content 48.0% lower and silver content 41.5% lower than the grades of the ore processed in the pilot plant.