A MULTIPHASE FLUID-MECHANICS APPROACH TO GAS HOLDUP IN BATH SMELTING PROCESSES

In slag-based, smelting-reduction processes, the overflow of slag from the vessel is considered a major limitation to productivity; this phe nomenon is commonly called slag foaming. While much has been learned f rom laboratory-scale studies of foaming, the superficial gas velocitie s are well below those encountered in production (centimeters per seco nd compared to meters per second). A multiphase fluid dynamic model wa s developed to determine the relationship between gas velocity and voi d fraction (holdup) at industrial production rates. In the model, the drag between the gas and slag is balanced against the weight of the sl ag. Within the framework of the model, the only unknown quantity is a drag factor which can be extracted from experimental data. Values of t his factor from water models, smelting-reduction converters, and other slag systems fall in a narrow range. The model can be used to estimat e slag height in smelting-reduction vessels. The behavior of slags at high rates of gas injection is markedly different from foaming observe d at low flow rates.