A Heat and Mass Transfer Model of a Silicon Pilot Furnace

Abstract

The most common technological route for metallurgical silicon production is to feed quartz and a carbon source (e.g., coal, coke, or charcoal) into submerged-arc furnaces, which use electrodes as electrical conductors. We develop a mathematical model of a silicon furnace. A continuum approach is taken, and we derive from first principles the equations governing the time evolution of chemical concentrations, gas partial pressures, velocity, and temperature within a one-dimensional vertical section of a furnace. Numerical simulations are obtained for this model and are shown to compare favorably with experimental results obtained using silicon pilot furnaces. A rising interface is shown to exist at the base of the charge, with motion caused by the heating of the pilot furnace. We find that more reactive carbon reduces the silicon monoxide losses, while reducing the carbon content in the raw material mixture causes greater solid and liquid material to build-up in the charge region, indicative of crust formation (which can be detrimental to the silicon production process). We also comment on how the various findings could be relevant for industrial operations.

Melting and dripping of a heated material with temperature-dependent viscosity in a thin vertical tube

“…1998; Sloman et al. 2017). The interface is not smooth, and there can be hanging filaments of material which will drip off.…”

“…Silicon is commonly produced in submerged arc furnaces (Valderhaug & Sletfjerding 1991; Valderhaug 1992; Schei, Tuset & Tveit 1998; Sloman et al. 2017), where the oxidisation of quartz rock (SiO) by lumps of carbon is driven by the heat from electrodes (Halvorsen, Schei & Downing 1992; Schei et al. 1998; Myrhaug, Tuset & Tveit 2004; Kadkhodabeigi, Tveit & Johansen 2011).…”

“…We examine these hypotheses by developing a thermo-mechanical model of furnace crust, using the simplified cylindrical geometry of experimental furnaces used by Elkem ASA, known as ‘pilot furnaces’ (Sloman et al. 2017). Annotated images of pilot furnace experiments are shown in figure 1.…”

“…1998), and convert to solid silicon carbide particles through the reaction (Sloman et al. 2017). Assuming molar volumes (Sloman et al.…”

Prediction of re-oxidation behaviour of ultra-low carbon steel by different slag series

“…It is of great practical significance for the researchers and operators to optimize the process parameters and improve production efficiency. Recently, some scholars [13][14][15][16][17] proposed some kinetic models, based on thermodynamic theoretical calculation and fluid dynamics equations, which can successfully predict changes in slag, liquid steel, and inclusions at the slag-metal interface. However, these models also have problems, such as decreased prediction accuracy and incomplete prediction of actual production requirements, that accompany changes in thermodynamic data and complex slag systems [18][19][20] .…”