ESTUDO DA INTENSIDADE DE CREPITAÇÃO DE MINÉRIOS GRANULADOS DE MANGANÊS DO BRASIL

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

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, wich has not been studied adequately yet. This work presents a physical, chemical and mineralogical characterization of the manganese lump ore from the three main Brazilian mines, Azul, Morro da Mina and Urucum, as well as their decrepitation behavior. The chemical analyses were made by AES-ICP and titration, the mineralogy cal characterization was obtained by optical microscopy and X-ray diffraction. The physical properties studied included density, surface area and porosity measurements. The samples were then characterized for decrepitation, according to the ISO8731 standards, with the exception of the grain size range, kept in this case between 19 and 6,3mm. The influence of the moisture and the thermal treatment of the samples, on the decrepitation behavior, was also studied. For the grain size range between 19 and 6,3mm, used at the decrepitation studies, the lump ore samples from Azul (MG60), Urucum (GU) and Morro da Mina (GMM) displayed very distinct chemistry. The contents of Mn, Fe and SiO2 for MG60 are 46.96; 4.12 e 3.99%, respectively. For GMM the contents are 24.48; 2.89 e 23.02%, and for GU they are 32.58; 6.92 e 2.11%. The Urucum lump ore presents the highest structural density (4.41g/cm3), followed by the Azul lump ore (4.02g/cm3) and by Morro da Mina (3.66g/cm3). The typological classifications of the ores are: anhydrous-oxide for Urucum, hydrated-oxide for Azul, silicate-carbonate for Morro da Mina. At the thermogravimetrical analyses, the mass losses were related to the thermal decomposition of oxides (cryptomelane, pyrolusite and braunnite), of carbonates (rhodochrosite) and of the hydrated constituents (mainly todorokite and anphibolites). There is a significant difference amongst the decrepitation intensity observed for the lump ores from Azul, Urucum and Morro da Mina. The oxide ores from Urucum (I-6.3mm = 10%) and Azul (I-6.3mm = 6%) present a high susceptibility to decrepitation, whilst thesilicate-carbonate from Morro da Mina shows no decrepitation. The presence of moisture increased the decrepitation intensity of the Azul and Urucum lump ores. The lab scale thermal treatment, at 200C for 48 hours, reduced in more then 60% the decrepitation indexes of both ores.

ASSUNTO(S)

1. crepitação - teses. 2. minérios de manganês - teses. 3. ligas de ferro - teses. i. universidade federal de ouro preto. escola de minas. ii. título. engenharia de materiais e metalurgica

ACESSO AO ARTIGO

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