Cold model experiments were performed to make clear the critical condition causing the entrapment of slag under bottom gas injection. Entrapment of slag was judged from visual observation. The following empirical correction of the critical liquid velocity on the centerline of the vessel. ucl, c was derived.
dB/D<Hs/D<1/2, 0.6<ρs/ρm<1, 0.3<νs/νm<120,
45 mN/m<σms<63 mN/m
ucl, c=1.2 urP-0.28
where, g: the acceleration due to gravity,
Qa, c: the critical gas flow rate for the entrapment of slag,
Hm: the thickness of metal layer,
σms: the interfacial tension between slag and metal,
ρs', ρm: the densities of slag and metal,
νs', νm: the kinematic viscosities of slag and metal,
Hs: the thickness of slag layer,
D: the bath diameter,
dB: the bubble diameter.
This correlation could predict the critical gas flow rate Qa, c for previous hot model experiments as well, provided that the flow pattern in the baths were similar to the present case.