Evaporation Mechanism of As and Sb from Liquid Steel Containing C and S

Abstract

The accumulation of tramp elements in ferrous scrap has become increasingly important in the steel industry as the consumption of ferrous scrap is rising due to the depletion of high-quality iron ore and increasing iron ore prices. In order to utilize scarp by evaporation refining, evaporation of As and Sb in liquid iron was investigated by conducting several liquid-gas experiments using an electromagnetic levitation melting technique. The evaporation rate of As and Sb were examined under various conditions (flow rate of gas, initial C and S concentrations). It was found from several kinetic analyses that S in liquid iron partly accelerated the evaporation rate of As and Sb by increasing the available S for forming the sulfide gas species, which are volatile, but partially decelerated the evaporation rate due to blocking evaporation sites. C in liquid iron partly accelerated the evaporation of Sb by increasing the activity coefficient. Based on the elucidated mechanism, an evaporation model equation for As and Sb was developed in the present study, which considers (1) species of evaporation, (2) surface blocking by S using ideal Langmuir adsorption, and (3) the effect of C and temperature on the activity coefficients of As, Sb and S.