Circuito alternativo para flotação de minério willemítico

Abstract

The present investigation addressed the search for an alternative circuit for the flotation of the willemitic zinc ore from Vazante, MG, aiming at an increase of the zinc metallurgical recovery without loss of the quality of the final concentrate. The methodology included size, chemical and mineralogical characterization, bench scale flotation experiments, and industrial tests. The characterization showed a high degree of liberation of willemite with respect to the gangue minerals. The laboratory experiments indicated that a significant proportion of the willemite particles present a high flotation kinetic rate, findings that lead to tests of an alternative industrial circuit, the feed being changed from the rougher to the cleaner stage. The initial results were not satisfactory.Operation adjustments were necessary, namely: increase in the conditioning residence time, reduction of the forced air flow rate in the cleaner and cleaner scavenger stages,and improvements of the agitation system, enhancing the contact between the descending willemite particles and the ascending air bubbles flow. The metallurgicalresults were overall recovery increase from 85.3% to 88.0%, the zinc grade in the concentrate being kept at 43.5%, and increase in the flotation circuit throughput from 98t/h to 120t/h.