Chemical wear analysis of a tap-hole on a SiMn production furnace

Silicomanganese (SiMn) is an alloy used in steelmaking to provide both Si and Mn additions at low carbon contents. In South Africa, SiMn is produced in three-phase alternating current (AC) submerged arc furnaces (SAFs) by carbothermic reduction of manganese ores in the form of lump, sinter, and briquettes (Steenkamp and Basson, 2013). In a SAF the electrode tips are submerged in a porous charge mix, with electrical energy being liberated by microarcing to a slag-rich coke bed floating on top of a molten metal bath (Olsen and Tangstad, 2004; Matyas et al., 1993). Typical power ratings for SAFs producing SiMn are 15–40 MVA; such furnaces produce 80–220 t of metal per day (Olsen and Tangstad, 2004). The furnaces are circular, with an external diameter of 11.6 m and height of 6.2 m being typical of a 40 MVA furnace (Brun, 1982). The initial report on the tap-hole wear profile and thermodynamic calculations conducted to understand the potential for chemical reaction as wear mechanism in the tap-hole area was presented at the SAIMM Furnace Tapping Conference (Steenkamp et al., 2014). The paper presented here expands on the previous work by including masstransfer calculations to estimate the possible extent of wear by chemical reaction.