Kinetic Studies on the Rate of Reaction between Molten Slag and Metal with Gas-injection Stirring

Abstract

Kinetic studies have been made on the rate of reaction between molten slag and metal with gas-injection stirring. The explored reaction is oxidation of Si in molten Cu by FeO in a Li₂O-SiO₂-Al₂O₃-FeO slag taking place under the condition of rate-controlling by Si transport in the metal phase. Kinetic experiments were done at 1250°C. The slag-metal bath was stirred by Ar gas injected through a nozzle located at the crucible bottom. The apparent metal-side mass-transfer coefficients of Si, k_Si', are calculated from the kinetic data. Relations between k_Si' and experimental conditions (gas flow-rate, V_g ; metal depth, h_M; slag depth, h_sl ; crucible diameter, d_c) have been investigated.
k_Si' is found to increase generally with increasing V_g. The dependence of k_Si' on the gas flow-rate varies at certain gas flow-rates denoted by V_g^* and V_g^**.In the low V_g range (V_g<V_g^* : Region I), k_Si' is proportional to ( V_g/d_c²)^1/2. In the medium V_g range (V_g^* <V_g<V_g^** : Region II), the effect of the increase in gas flow-rate on k_Si' is cosiderably smaller than in Region I. In the high V_g range (V_g>V_g^**: Region III), the extent of the increase in k_Si' with V_g increases again. It is also found that k_Si' increases with metal depth, h_M, below a transitional depth, h_M^*. Above the transitional metal depth h_M^*, k_Si' becomes independent of h_M. Examinations have been performed of the influence of slag depth, h_sl, on k_Si' in Regions I and II. In Region I, k_Si' is independent of h_sl. In Region II, k_Si' decreases with the decrease of slag depth.