Behavior of slag foaming with reduction of iron oxide in molten slags by graphite

Behavior of slag foaming was investigated under the condition of iron oxide reduction by graphite in CaO-Li2O-SiO2-Al2O3 slag systems. Experiments were carried out at 1573 K, under Ar gas atmosphere with a flow rate of 1000 N cm(3)/min. The SiO2 molar fraction of the primary slag was varied between 0.33 and 0.49. The initial concentration of iron oxide in the molten slag was varied between 3 and 15 mass%. The content of sulfur ranged from 0 to 0.68 mass%. The rotation speed of graphite rod was kept constant at 1.67 s(-1). The slag foaming is evaluated by the ratio of the volume of the gas contained in slag to the total volume of foaming slag, namely gas holdup, epsilon. The slag foaming is mainly affected by the CO gas evolution rate. The slag is not foamed when the CO gas evolution rate is less than a critical value. Then with the increase in CO gas evolution rate, the slag foaming becomes vigorous and approaches to a plateau value. Addition of sulfur suppresses the slag foaming and silica favors slag foaming a little. A simple fluid mechanics model, called drift-flux analysis, can be used to fit the present experimental results.