Characteristics of Na₂CO₃ Slag in the Refining of Hot Metal with Oxygen Top-blowing

Abstract

Change in chemical composition of slag during the refining of hot metal with Na₂CO₃ under the condition of top-oxygen blowing in the temperature range from 1 280 to 1 450°C was studied.
Violent decomposition of Na₂CO₃ in the presence of [C] was observed at the beginning of experiments. However, total amount of Na evaporated from slag during the experiment was not conspicuous. Rate of vaporization of Na was found to decrease with decreasing reaction temperature and with increasing contents of acidic compounds in the slag, such as SiO₂ and P₂O₅.
Judging from material balance calculation for S, some part of charged S was considered to be transferred to waste gas. Chemical analysis of the dust and slag indicated that the preferential vaporization of S and Na from the slag occurred. Vaporization loss of P was not detected by chemical analysis of dust and slag. However, the study with thermal-balance showed that Na₃PO₄ reacted readily with graphite and converted to CO, P and Na above 1 000°C.