Produção de concentrado de zinco a partir de minério silicatado com redução no teor de carbonatos

Abstract

The zinc world reserves, are estimated in 482 millions metric tons of metal content. The reserves of five countries, Australia, Canada, Kazakhstan, China, and USA represent over 70% of the world total. The major Brazilian reserves (89%) are located in Minas Gerais state, Vazante and Paracatu, 4,900 metric tons, representing 1% of the world total. The ore from Vazante´s deposit contains the zinc silicate willemite, and dolomite as the major gangue mineral. The ore is sent from the underground mine to the concentrator for the stages of crushing, grinding, zinc flotation, carbonates flotation, thickening, and filtration. Alternative concentration routes were investigated in the search for increases in the zinc grade and recovery and reduction of the contaminants carbonates and magnesium in the concentrate. The selected routes were pre-concentration via ore sorting and heavy media separation and carbonates flotation including laboratory and pilot scales experiments followed by an industrial trial. The behavior of the heavy media separation was more uniform, yielding lower zinc losses in the case of richer ore, tailings with zinc grade below 2%, and zinc recovery at 99.44% and average zinc content in the concentrate 24%, for feed grade 15.54%. Results of ore sorting varied with the feed rate, some tests yielding poor results, good performance being observed in other tests. The carbonates flotation studies indicated that the collecting action of the fatty acids soaps is strongly affected by the saponification degree, which should be at least equal to 189 mgKOH/g. In the industrial trial the carbonate content decreased from 11.00% to 10.06%, representing a gain of 8.55%. The average MgO grade in the concentrate decreased from 3.69% to 3.02%. The zinc metallurgical recovery of the circuit including carbonates flotation was 89.82%, representing an increase of 3.75% with respect to the value of 86.57% achieved in the original circuit, in the absence of carbonates flotation.