Physical simulation of impurity removal through submerged liquid slag injection in steel melt

Abstract

With the increase in demand for quality steel having very stringent compositional control, the secondary steelmaking has become one of the significant developments in the steel making technology during the past few decades. Injection of powder with inert carrier gas is commonly practiced in industry to decrease the impurity contents of steel in a more economical way. Such high temperature metallurgical operations are mass transfer controlled and accordingly the design and operating parameters have significant roles to play. However, powder particles can only penetrate partially to the liquid melt while most of the particles ascend through the melt as "particles inside the bubble" in the semi-solid state without contributing much to mass transfer. In this regard submerged liquid slag injection may be considered as a potential area of investigation. In the present study, simulation of the submerged liquid slag injection in steel melt has been carried out using a cold model in the laboratory. Relative contributions of the transitory to permanent contact reactions have been estimated from several experimental data in conjunction with the mathematical model proposed by Ohguchi and Robertson. The present results show that mass transfer rate increases with increase in gas flow rate, liquid injection rate and lance depth. An empirical correlation for overall mass transfer rate constant as a function of gas flow rate, oil injection rate and lance depth has been developed. The present result also indicates that transitory contribution increases significantly with increase in gas flow rate.