Abstract The mineral processing of low-grade iron ores commonly generates large volumes of slime, which are disposed as tailings. Modern mining requires strives to eliminate the use of tailings dams in a maximum effort to increase metallurgical recovery, the security and reduction of the operational cost. This research aims for the recovery of iron contained in the slime, which consists of a material with 38% Fe and <40 µm, originating from the desliming cyclones. Pilot tests were performed on the Wet High-Intensity Magnetic Separator (WHIMS) and on the Vertical Ring Pulsating High Gradient Magnetic Separator (VPHGMS) considering different configurations in terms of operating parameters and routes. The best results were obtained for VPHGMS with an iron content in the concentrate of 67.06% and mass and metallurgical recovery of 32.42% and 56.86%, respectively. In the best condition tested, around 540 thousand tons of concentrate can be incorporated into production and has great environmental relevance.

Visando a melhorias no beneficiamento e no processo de fabricação de ferroligas de manganês, foi realizada a caracterização de uma tipologia predominante de minério de manganês, de ocorrência na região de Carajás, PA, BR. Obteve-se uma amostra representativa da tipologia e foram realizadas análise granulométrica por peneiramento e análise química, por ICP-AES. Foram identificadas por difratometria de raios X as fases minerais majoritárias. Um estudo termogravimétrico foi desenvolvido para verificar a estabilidade térmica, ao ar, das fases minerais majoritárias. Observou-se que 19,3% da amostra encontram-se abaixo de 6,3mm. O teor de manganês no minério foi de 52,63% em peso, com 1,92% de sílica, 0,17% de fósforo e 3,13% de ferro. Foram identificados, na amostra, os óxidos de manganês criptomelana, todorokita e pirolusita, com goethita, quartzo, gibbisita e caolinita compondo a ganga. Para a amostra estudada, observou-se a decomposição térmica dos óxidos criptomelana e pirolusita, em torno de 600ºC, ao ar. Em torno de 950ºC, teve início a transformação de Mn2O3 em Mn3O4.

In order to improve manganese-iron alloy production processes, an important Brazilian manganese ore typology, placed in Carajás, PA, was characterized. A representative sample was obtained from mine. The particle size determination was performed by screening, followed by chemical analysis using plasma spectrometry (ICP-AES). The physical properties studied included density, surface area and porosity measurements (BET). The mineral constituents was identified and quantified by X-ray diffraction. A termogravimetrical study was done in order to verify the thermal stability of major mineral constituents in the air. It was observed that 19.3% of studied typology was below 6.3mm. The manganese, silica and phosphorus contents were 52.63%, 1.92% and 0.17%, respectively. The oxides identified were cryptomelane, todorokite and pyrolusite. The other constituents were goethite, quartz, gibbsite, and kaolinite. According to the thermal study, the cryptomelane and pyrolusite start their decomposition in the air, at approximately 600ºC. At around 950ºC, Mn2O3 decomposition and Mn3O4 growth were observed.

Crushing residues of FeSiMn and high-carbon (HC) FeMn alloys were characterized in order to evaluate their recycling possibility. Particle size determination was performed by screening, followed by chemical analysis of each particle size range using plasma spectrometry (ICP-AES). The slag content was identified and quantified by optical microscopy. All of the fines with grain sizes above 1.18 mm presented alloy contents in excess of 99 wt. (%) and were determined to need no further concentration prior to recycling. However the contents of Mn, Fe, Si and P in the fraction below 1.18 mm did not meet the chemical specifications for commercial manganese alloys, except for phosphorous. Optical microscopy of the fraction below 1.18 mm, showed that 87.95% of the FeSiMn corresponded to the alloy and that the slag content was 12.05%. For the HC-FeMn sample, 95.07% corresponded to the alloy and only 4.93% to the slag. These results revealed potential for gravity concentration and recycling, reducing the residues in about 95% and improving the process productivity.

Esse artigo apresenta estudos de concentração de finos de minério de manganês (estocados como rejeito) da Mineração Morro da Mina/RDM em mesa oscilatória, visando à obtenção de concentrados para serem empregados na indústria metalúrgica. Os teores de Mn, na amostra global e nas frações acima e abaixo de 0,074 mm, eram de 28,30; 26,84 e 31,31%, respectivamente. Pela análise granulométrica, verificou-se que 80% desses finos encontravam-se abaixo de 0,149 mm. Nas condições otimizadas dos ensaios de concentração (15% de sólidos na polpa e ângulo de inclinação da mesa igual a 3º), foram obtidas recuperações de manganês da amostra global, acima e abaixo de 0,074 mm de 77, 81 e 62%, respectivamente. Os teores de manganês e impurezas, nos concentrados, para as amostras estudadas, satisfizeram as especificações químicas dos produtos comercializados pela empresa.

This article presents the results of fine manganese ore from Morro da Mina Mine/RDM concentration studies using oscillatory table in order to obtain concentrates to be used in metallurgical industries. The global, the fractions above and below 0,074 mm samples manganese contents were 28,30; 26,84 and 31,31%, respectively. It was observed that 80% of the particles in global sample were below 0,149 mm. For the optimized table concentration test, solids pulp with 15% and table inclination angle of 3º, the manganese recoveries of the global, fraction above 0,074 and below 0,074 mm samples were of 77, 81 and 62%, respectively. The manganese and impurities contents in those concentrates satisfied the chemical specifications of Morro da Mina Mine/RDM products.