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UBC Theses and Dissertations

Development of slag-resistant refractory linings Sarkar, Dipankar


Attempts have been made to develop slag resistant refractory lining for Dore furnaces, which are primarily used for smelting Pb-anodes in order to extract precious metals. All the physical properties of Dore slag (PbO-based) such as, melting temperature, melt density, viscosity, surface tension and wetting behaviour over the temperature range of furnace operations (600-1100°C) were determined. These studies indicated that Dore slags (i) melt at temperatures between 550 and 600°C; (ii) have the melt densities 5.0 to 7.0 g/cm³ in the temperature range 750-1050°C, melt density primarily being controlled by the concentration of Pb0(ρ20°C-8.0/cm³) and Bi₂O₃ (ρ20°C-8.9/cm³) (iii) are highly fluid in the temperature range 750-1050°C, having the viscosity of 0.4 to 0.8 N.S.m⁻²; (iv) have low surface tension values 450 to 325 dyne.cm⁻¹ at 750°C and (v) have low contact angles between 15 and 30° on alumina substrates. These slag properties indicate that the slags would spread very easily on alumina refractories and most possibly on other refractories. Coating compositions were then developed by studying the available phase equilibrium diagraim/s, with the consideration that a glassy component would be necessary in the coating to seal-up the pores. Slag pill tests on coated bricks revealed that only application of a coating could not prevent significant slag prenetration. This is so in spite of the fact that the coating compositions contained 60-70 silica to form a large amount of glassy phase in the coating. To reduce the harmful effect of slag constituents, CaO was found to be the best oxide to produce high temperature melting compounds by reacting with oxide constituents in slags. Further studies on impregnating the bricks with CaO and CaCl₂ show that an optimum impregnation of bricks with ~ 2 wt.% CaCl₂, and a coating of a mixture of 30% CaO, 60% SiO₂ and 10% slag on the impregnated bricks, have been able to stop slag penetration into the refractory bricks.

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