Reduction of Manganese Ores by Methane-containing Gas

Abstract

Reduction of Groote Eylandt (Australia) and Wessels (South Africa) manganese ores using CH 4 -H 2 -Ar gas mixture was investigated in a fixed bed laboratory reactor in the temperature range 1 000-1 200°C. The extent and kinetics of manganese ore reduction as a function of gas composition and temperature were determined by on-line off-gas analysis using mass-spectrometer and dew point sensor. Morphology of ores and its change in the course of reduction was examined by optical and scanning electron microscopy. Phases of raw materials and reduced samples were analysed by XRD and EPMA.Manganese and iron oxides were reduced to carbide (Mn, Fe) 7 C 3 . High extent and rate of reduction by methane-containing gas in comparison with carbothermal reduction were attributed to high carbon activity in the reducing gas, which was in the range 15-50 (relative to graphite). The reduction rate of Wessels manganese ore increased with increasing temperature. Reduction rate and extent of Groote Eylandt manganese ore achieved maximum at 1 050°C. The decrease in rate and extent of reduction of Groote Eylandt ore at higher temperatures, particularly at 1 150-1 200°C, was due to sintering and formation of semi-liquid silicate slag. An addition of lime (10-15 mass% CaO) to the Groote Eylandt manganese ore increased melting temperature of slag and significantly increased the rate and extent of reduction at elevated temperatures.

Carbothermal Solid State Reduction of Manganese Ores: 2. Non-isothermal and Isothermal Reduction in Different Gas Atmospheres

“…Formation of a liquid phase in the process of reduction of Groote Eylandt ores was a significant factor affecting the ore reduction. In reduction of GE-PF ore by methane containing gas studied by Anacleto et al, 20) extent and rate of reduction significantly decreased with increasing temperature from 1 100°C to 1 200°C; degree of reduction of this ore at 1 200°C was slightly above 50 % after 5 h of reaction. This was attributed to the formation of a liquid phase and decrease in the interfacial reaction area with blockage of methane-hydrogen gas access to the ore interior.…”

“…Doping of the GE-PF ore with lime (10-15 % CaO) increased the ore melting temperature and significantly enhanced reduction rate and extent at 1 200°C. 20) Carbothermal reduction behaviour of GE ores was very different from that observed in reduction by methane-containing gas. The major difference between these processes is obvious: carbon is intimately mixed with oxides in the carbothermal reduction, while in reduction by CH 4 -H 2 gas, carbon is delivered to the ore interior from the gas phase.…”

04/00129 Oxidative coupling of methane

“…As discussed before, the higher that ratio, the more active is the catalyst because more oxygen is exposed on the catalyst surface to be converted. which coexist on the catalyst surface [121]. We also found that the total amount of stored oxygen, which has to be released for reduction of Mn 2 O 3 into MnO, was never reached.…”

“…However, the findings of Jones et al indicate that also the manganese oxide is able to form active sites for the selective activation of methane [122]. As reported by other groups, supported manganese oxides tend to form also deep oxidation products [121,123,112], Therefore, the proposed redox mechanism of Jiang et al has to be extended according to equations (43)- (45), which considers further redox activity of manganese oxide, as the total oxidation reaction of methane and also a selective activation. However, due to the fact that even small amounts of Na 2 WO 4 enhances the methane conversion and the C 2 selectivity, the reaction rates of equations (38) - (42) must be higher compared to the reaction rates in equations (44)- (45).…”

“…775 °C) a phase change of Mn 2 O 3 to Mn 3 O 4 was observed, which also indicates a loss of oxygen [121]. The influence of the film thickness on the oxygen storage capacity is presented in Figure 27 B.…”