Control of open slag bath furnaces at Highveld Steel and Vanadium Ltd : development of operator guidance tables

Abstract

Several electric furnaces, which are used to melt down partially prereduced vanadiferous magnetite at Highveld Steel and Vanadium, have recently been converted from submerged arc furnaces (SAFs) to open slag bath furnaces (OSBFs). The self-regulating nature of SAFs is largely absent from the OSBFs, and hence the OSBFs rely more strongly on process control. As a first step towards implementing a process control system, a mass and energy balance was drawn up for the OSBFs, and this was used to develop operator guidance tables. The tables show the required changes in feed rate and power, to accommodate changes in prereduction, and to correct overcharged and undercharged furnace conditions. Implementation of the tables has contributed to improved process stability.