The sheer diversity of tapping configurations used on industrial pyrometallurgical operations is at first bewildering. They range from historical tilting furnaces without tapholes to modern eccentric bottom tapping (EBT) tilting and/or bottom slide-gate electric arc furnaces; to classical single tap-hole multiphase tapping (e.g. metal/matte and slag); to dedicated phase tap-holes (e.g. dedicated metal/matte-only and slag-only); to dedicated phase multiple tap-hole configurations (up to eight metal/matte-only tap-holes and six slag-only tap-holes); to more esoteric metal/matte-only siphons and slag overflow skimming, e.g. Mitsubishi Continuous Process (Matsutani, n.d.). This can be further complicated by periodic batch tapping; consecutive tapping on a given taphole; alternating tap-hole tapping practice; near-continuous slag-only tapping, with discrete batch matte/metal tapping on higher productivity, but low metal/matte fall (<20% by mass feed) Co and Ni ferroalloy and platinum group metal (PGM) matte furnaces; near-continuous tapping through batch tapping of individual tap-holes that are opened consecutively Post et al., 2003); to fully continuous tapping on coupled multi-furnace cascades (Matsutani, n.d.). This is largely a consequence of differing processing conditions (process temperature, superheat ( T), Prandtl number, Pr = C P /k, where = dynamic viscosity, C P = specific heat capacity and k = thermal conductivity, and resulting heat flux). But this can also be influenced strongly by industrial operating philosophy in terms of furnace design for campaign life longevity (i.e. greater capital expenditure for longer, say 20-30 years' life) versus furnace productivity (i.e. number of heats/campaigns to provide the greatest possible dilution of fixed costs per unit of commodity produced). And this may not even be consistent within a given commodity; all ironmakers (blast furnace (BF) campaign lifebased) supply downstream steelmakers (who use heat/campaign-based converters and/or electric arc furnaces).However, regardless of the specific taphole configuration or operating philosophy, owing to the addition of dynamic (often periodic) and more intense process conditions (exposure to higher temperatures leading to accelerated corrosion, greater turbulence, and elevated rates of mass and heat transfer) and higher concomitant thermomechanical forces (from thermal or flow shear stresses), furnace performance and longevity is intimately linked to tap-hole performance. The tap-hole -key to furnace performance by L.R. Nelson* and R.J. Hundermark † The critical importance of tap-hole design and management for furnace performance and longevity is explored through examining some of the specific matte, metal, and slag tapping requirements of non-ferrous copper blister and matte converting and smelting, ferroalloy smelting, and ironmaking systems. Process conditions and productivity requirements and their influence on tapping are reviewed for these different pyrometallurgical systems. Some critical aspects of the evolution ...
Electric smelting furnaces typically consist of a refractory shell incorporating strategically placed water-cooled copper components for maintaining furnace integrity. Over time, both the refractory lining and water-cooled copper components can undergo deterioration and wear, resulting in potential failure in the form of a furnace run-out, where furnace matte and/or slag leaves the furnace in an uncontrolled manner. With smelting occurring at extreme temperatures, large amounts of conventional thermocouples and new fibre optic technology (for copper) and resistance temperature detectors (for cooling water) are used to continuously measure the temperature of the furnace crucible lining with the aim of ensuring safe operation of the furnace. Measurements from these numerous sensors are typically recorded at high frequency, with data overload of operators and metallurgical staff alike commonly occurring.Monitoring of the furnace temperature measurements, which is pivotal to furnace integrity monitoring, has traditionally been accomplished through the use of alarm and trip limits set on individual temperature measurements of the copper coolers, their cooling water and refractory, with limits typically defined based on design criteria and not on current operating conditions. Due to the changes in furnace operating conditions and the sheer number of temperature measurements available on a furnace this often proves to be very ineffective, except when large upset conditions occur; and the warning is then often too late.When Mortimer Smelter, a platinum group metal (PGM) concentrate smelting operation located on the western limb of the Bushveld Complex, changed its cooler design to novel graphite-protected shallow-cooled composite copper coolers with graphite-protected deepcooled copper lintel coolers, the furnace was at some risk due to the new design. In order to confirm that maintenance could take place as planned, an alternative temperature monitoring strategy was required. Multivariate statistical data-based techniques, proven to be effective in circumventing the previously mentioned monitoring inadequacies through data compression, dimensionality reduction, and the handling of noise and correlation (Venkatasubramanian et al., 2003), were considered as the foundation of such a strategy. In this paper we discuss the development of and operating experience from a multivariate statistical data-based system for monitoring furnace temperature measurements. Further application of the system so developed, informing a decision to delay a matte endwall rebuild on the Polokwane Smelter, is also described.Furnace integrity monitoring using principal component analysis: an industrial case study by J.W.D. Groenewald*, L.R. Nelson*, R.J. Hundermark † , K. Phage*, R.L. Sakaran*, Q. van Rooyen*, and A. Cizek* Furnace temperature monitoring, the cornerstone of furnace integrity monitoring, has traditionally been accomplished using alarm and trip limits set on individual temperature measurements of the copper coolers and refractory, ...
The history and variety of commercial Platinum Group Metal (PGM) matte converting processes are explored. Aspects unique to pneumatic converting of high iron, lower grade mattes (typically up to 30% NiCuCo), often containing chrome (0.5-2% Cr 2 O 3 ), to PGM-enriched (1500-25000 g/t PGM) converter mattes, to endpoints specific to promote downstream refining to final metal are described. The range of converter vessels, involving batch, to staged, to continuous converting processes are presented, along with some of the operating requirements and challenges.
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