The electric arc furnace has characteristics which make it attractive for a number of metallurgical applications. Some of these characteristics are: high thermal efficiency, the possibility of attaining very high temperatures, low off-gas volume compared to fuel-fired furnaces, no impurities are introduced by the heat source, and impurities in only minor amounts are introduced by the electrodes. It also has disadvantages, the chief ones being the relatively high cost of electrical energy compared to fossil-fuel energy and the fact that, when oxide ores are smelted using carbon as reductant, the off-gases emitted are rich in carbon monoxide.
The vital components of the shaft-electric furnace are: the arc furnace, the feed-control mechanism between the arc furnace and the shaft furnace, the shaft furnace and its associated feed system, and an exhaust system capable of exhausting all the gaseous products from both the arc furnace and shaft furnace. In order to maintain countercurrent flow in the shaft, with solid charge descending and gases ascending, it is necessary that the exhaust system maintain a reduced pressure at the top of the shaft, thus it must be connected to the top of the shaft, adjacent to the incoming feed.
The 250-kVA arc furnace was