Sub-electrode gap and specific electrical resistance of a ferroalloy furnace bath

To increase the energy-technological efficiency of a ferroalloy furnace, the author studied the smelting of 45 % ferrosilicon by a carbon-thermal method. In some cases, methods for measuring and changing the specific electrical resistance of charge materials at temperatures up to 1900 K are used to study the technology of smelting ferroalloys for smelting manganese alloys from various ores, carbonaceous ferrochrome, ferrosilicon, ferrosilicon manganese and ferrosilicon aluminum. For a series of heats of 45 % ferrosilicon, measurements of the useful voltage, electrode current, and power factor were carried out. As smelting progressed, the bath resistance was calculated and for the reaction melting zone (melting crucible), the specific electrical resistance in the single-electrode version of the furnace was determined at various sub-electrode gaps. Smelting using technology with an increased sub-electrode gap was performed in a large-scale experimental electric furnace with a capacity of 130 ‒ 290 kV·A. As a result, it was found that an increase in the sub-electrode gap from (0.6 ÷ 0.9) to 6.0 of electrode diameters leads to the effect of a 2.5-fold increase in resistance, voltage and power in the bath (each indicator), but at the same time to a slight decrease in the specific electrical resistance of the melting zone of the furnace with a constant diameter (150 mm) of the electrode. The optimal sub-electrode gap (electrode – substrate distance) in the bath of a single-electrode furnace was determined by changing the specific electrical resistance. The optimal value is 3.33 of the electrode diameter. Assuming deviations of about ±5 % of this value, it is possible to efficiently smelt 45 % ferrosilicon in the range of 3.2 ‒ 3.5 electrode diameters for the sub-electrode gap during the ore recovery process with a closed arc.