Critical Condition for Formation of Accretion at Gas-Injection Nozzle Tip and Cooling Capacity of Gas

Abstract

A study has been made on the formation of accretion at the nozzle tip during submerged gas injection into Fe-C liquid metal. Experiments in 1 ton heating furnace were carried out to obtain data required for the initiation of the accretion and the followings were resulted: The inner diameter of gas injection nozzle and the solidus temperature of Fe-C were found to be determining factors for the critical condition for the formation of the accretion. By using Ohguchi’s heat balance equation for the stability of the accretion, transfer coefficient of the heat from hot metal to the accretion was estimated to be 63 ε ˙ 0.3 . Furthermore, by using modified Ohguchi’s heat balance equation including reaction heat term, the effective rate of reaction heat was obtained, which is 0.03 for CO₂ and 0.4~1 for C₃H₈. Plant scale experiments were also conducted in 270 LD convertor at Muroran Works in order to examine the effect of the blowing of CO₂-C₃H₈ gas mixture on the cooling for the protection of bottom nozzle and it was found that almost all of the reaction heat of C₃H₈ is contributed to the cooling, which supports the above mentioned result of 1 ton scale experiments.