Magnesite, apart from seawater, is the main feedstock for dead burned magnesia (DBM) production, one of the most important raw materials for basic refractories. Brazil produces, out of RHI Magnesita's plant located in the city of Brumado, a high density and high purity DBM from a floated magnesite concentrate. In order to increase the flotation process productivity, which bottleneck is the ball grinding operation, a different grinding approach was selected and evaluated in a pilot plant scale.The proposed comminution system comprises a primary grinding (open circuit with specific parameters) and a high-frequency screener, where the undersize feeds the first desliming and flotation circuit. This step produces a slurry with higher silica and natural slime, composed mainly by clay-minerals. On the other hand, the oversize follows a secondary grinding (closed circuit with hydrocyclones) and produces a slurry with less contaminants and a slime composed mainly by over milled magnesite, rich in MgO, feeding the second flotation circuit. This division creates specific conditions to work in the flotation parameters and, in the second case, to avoid desliming.Therefore, the benefits of this modification go beyond comminution capacity increase, as it can also improve the desliming and flotation recoveries and reduce the concentrate's impurities.The research aimed the study of flotation parameters in pilot scale such as pH and the desliming necessity for both circuits, evaluating the process in continuous operation.According to the pilot tests performed, the modification in the magnesite flotation unity could promote a 27 % increase in the productivity, where 17.6 percentage points (pp) was related to the increase in grinding capacity and 9.4 pp was due to yield improvement, promoted by 5.7 pp loss reduction in desliming and 3.7 pp led by yield increase in flotation. All these results were calculated using pilot plant results, and still, have to be confirmed in industrial scale.
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