Decrepitation of Brazilian manganese lump ores.

Abstract

A common problem in the production of ferromanganese alloys is the lack of knowledge about the mineralogical and metallurgical properties of the manganese lump ores. An important quality parameter of the lump ores is the decrepitation, which has not been studied adequately yet. This work presents physical, chemical and mineralogical characterizations of manganese lump ores from the three main Brazilian mines, Azul, Morro da Mina and Urucum, as well as their decrepitation behaviors. The samples, after characterization, were separated in three batches, one as received, the second after drying at 105°C, and the third after thermal treatment at 200°C. They were then tested for decrepitation at the temperature of 700°C for 30 min, with the particle size range kept between 19 and 6.3mm. The influence of the thermal history was studied together with the influence of the typological classifications of the ores, i.e., anhydrous-oxide for Urucum, hydrated-oxide for Azul, silicatecarbonate for Morro da Mina. A significant difference amongst the decrepitation behaviors was observed for the lump ores from Azul, Urucum and Morro da Mina. The oxide ores from Urucum (- 6.3mm = 10%) and Azul (-6.3mm = 6%) present a high susceptibility to decrepitation, whilst the silicate-carbonate from Morro da Mina shows no decrepitation. The presence of moisture increased the decrepitation intensity of the Azul and Urucum lump ores. The bench-scale thermal treatment reduced in more then 60% the decrepitation indexes of both ores.