Investigation of viscous fingering during blast furnace hearth drainage using a hele-shaw viscous flow model

Unexpected discharge of blast gas in the early stages of casting from a blast furnace has a significant impact on the furnace operations, resulting in premature plugging of the tap hole and consequently poorer stability, productivity and overall efficiency of the furnace. A physical modelling study has been carried out to understand the mechanism of the gas/slag interface instability during hearth drainage using a Hele-Shaw viscous flow model. Mineral oil and ZnCl₂ aqueous solution were used to simulate molten slag and iron, respectively. The research is aimed at exploring the possibility of viscous fingering being the cause of the premature emission of blast gas from the taphole. The experimental evidence showed that viscous fingering could take place, resulting in the premature release of the blast gas, if the gas/slag interface descending velocity in the region near the taphole is greater than the critical value for viscous finger formation. Viscous fingering is likely to cause the unexpected early blast gas discharge under certain hearth conditions during casting