Minerals, Vol. 15, Pages 968: The Effect of Ore Pre-Heating on the Operation of a 300 kVA Submerged Arc Furnace for High Carbon Ferromanganese Alloy Production—Pilot Study Results

Minerals doi: 10.3390/min15090968

Authors:
Matale Samuel Moholwa
Sello Peter Tsebe
Derek Hayman
Sanda Moloane
Joalet Steenkamp
Martin Sitefane
Driaan Bezuidenhout

The effect of ore pre-heating on the operation of a 300 kVA Submerged Arc Furnace (SAF) for high carbon ferromanganese (HCFeMn) alloy was investigated. The two types of Mn ores from the Kalahari Manganese Field (KMF) were used in the investigation (Ore #1 and Ore #2). Quartz and coke sourced from South Africa were used as a fluxing agent and a reductant, respectively. The Mn ores, reductant and fluxing agent were delivered to Mintek with a size range of +6–20 mm and were sent to our in-house laboratories to determine the chemical and physical properties. The samples were taken for Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), combustion method (LECO), proximate analysis and quantitative X-ray diffraction (QXRD). A newly designed and constructed pilot facility at Mintek was used in the investigation. The facility included a 1 t/h rotary kiln coupled to an electric arc furnace supplied with an alternating current (AC) with a 300 kVA tap-changer transformer. The main aim of the investigation was to demonstrate the effect of ore pre-heating to 600 °C on the furnace energy consumption and CO/CO2 emissions. The experimental approach adopted involved feeding Mn ore to establish baseline operating conditions, followed by feeding of Mn ore pre-heated with a rotary kiln to compare operational parameters. The pilot campaign experienced several operational challenges but there were periods of stable operation that enabled data collection for furnace energy consumption and CO/CO2 emissions. The effect of pre-heating the ore to 600 °C on the SAF energy consumption and CO/CO2 emissions was demonstrated successfully and revealed that energy savings and reduction in furnace CO2 emissions is achievable. Pre-heating Mn ore to 600 °C lowered the furnace energy consumption by an average of 22.5% and CO2 emissions by an average of 37%. The campaign also achieved an overall manganese recovery of 86%. Operating the furnace with hot feed increased the heat losses through the roof by 300% compared to heat losses observed during cold feed. There were also no significant changes in the furnace electrical parameters observed between the two feed modes.

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