C. Walker, T. Koehler, N. Voermann and B. Wasmund
INFACON XII, The Twelfth International Ferro alloys Congress , June 8, 2010. Helsinki, Finland
The productivity of FeNi smelting furnaces has risen steadily since the 1950’s with an accompanying improvement in energy efficiency and reduction in capital and operating costs per pound of nickel produced. These increases have been enabled by the introduction of copper sidewall cooling technology and the shielded-arc smelting process in the 1970’s and subsequent advances in furnace technology, control systems and operating practice. Although there are substantial benefits to be realized from increasing productivity there are also challenges in achieving steady operation at high power and throughput. Lessons learned from recent furnace operating experience has improved understanding of the key issues with respect to maintaining process stability, feeding and tapping the furnace, controlling the molten bath temperatures and chemistry, maintaining crucible and roof integrity and delivering power reliably and efficiently to the furnace under high voltage arcing conditions. These issues are analyzed and an understanding of the interaction between metal grade, calcine quality, power input per electrode, arc length and feed pattern on furnace operation and silicon reversion is presented using specific examples in context with their indirect effects on the crucible design and integrity. The effects of high power, arcing operation on power quality within the plant and on the power provider are also discussed. Finally solutions for further productivity and efficiency improvements in the immediate future are proposed.