The practice of adding alloying materials to amolten bath is an integral feature of many pyrometallurgicaloperations. However, very little is known about the dissolutionrate and solution mechanisms of solid additives in liquid melts. Infoundries where large tonnages of liquid metals are handled, thereis considerable interest in achieving optimum metal quality atminimum cost. This objective is influenced by several factors andthe solution is often plant specific. Though the amount, sequenceand mode of ferroalloy addition vary from plant to plant, variousfundamental factors determine how quickly these additionsdissolve in the bath. At the Ingot Mould Foundry (IMF) in TATASTEEL blast furnace hot metal is used to cast ingot moulds. Thecomposition of hot metal desired for making ingot mouldsdemands addition of 20 kg each of Ferromanganese andFerrosilicon in the 12 T transfer ladles into which the blast furnacemetal is poured at the IMF. Owing to low temperature of hot metalat the IMF, casting commences immediately and completedissolution of the ferroalloys is often not possible. To study thisaspect in detail and to evolve suitable corrective measures, amathematical model for the melting of a solid particle in a liquidmetal bath was developed at TATA STEEL. The model wasvalidated using the data available in literature. In keeping withpublished work, two separate dissolution periods were identified -a "shell period" and a "free dissolution period". The maximumthickness of the crust formed around a spherical particle shortlyafter immersion, can be obtained by using the mathematical modelwhich has been developed. The model can also be used toinvestigate the effect of various parameters such as superheat ofthe bath, size of the particle, ect., on the maximum crust thicknessand the particle melting time. On the basis of this study, theaddition of ferromanganese and ferrosilicon was optimized at theIMF in Tata Steel.
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