Slug flow in a blast furnace taphole

Excessive splashiness of a blast furnace taphole stream, which is caused by entrained blast air, can result in premature trough refractory wear. This splashiness has been found to occur when the gas–liquid flow regime of slug flow is present in the taphole tube. The taphole stream trajectories reported by He et al. [Q. He, P. Zulli, F. Tanzil, B. Lee, J. Dunning, G.M. Evans, Flow characteristics of a blast furnace taphole stream and its effects on trough refractory wear, ISIJ Int. 42 (2002) 235–242] can be predicted by the theory proposed herein that recognises that the average velocity in the liquid slug is equal to the sum of gas and liquid superficial velocities. The splashy flow observed by He et al. [Q. He, P. Zulli, F. Tanzil, B. Lee, J. Dunning, G.M. Evans, Flow characteristics of a blast furnace taphole stream and its effects on trough refractory wear, ISIJ Int. 42 (2002) 235–242] may be simply predicted by reference to a two-phase flow regime map. It is suggested that a splashy taphole stream will be avoided if the taphole points downwards or if the cast rate is above around 5 m s−1.