Manganese Distribution between a Slag and a Bath of Molten Sponge Iron and Scrap

Abstract

Sponge iron and scrap were charged and melted in a 70 ton UHP electric arc furnace. Samples of molten metal and slag were taken and the data obtained from their analysis were used to investigate the effects of some process parameters on the thermodynamics and kinetics of manganese oxidation.
The present work shows that the activity coefficient of (MnO) is mainly dependent on temperature and varies only slightly with the basicity. The partial molar enthalphy of solution of MnO in the slag is 45.3 kJ/mol. The activity of (MnO) varies linearly with the concentration in the temperature range from 1 550 to 1 670°C and basicity range between 0.63 and 3.82.
A linear relationship between the activity of [Mn] and the concentration upto about 1 wt% has been obtained, which shows that the average value of the activity coefficient is 0.9503.
The manganate capacity and manganese distribution ratio are influenced mainly by the temperature and slightly by the basicity.
The rate controlling step in manganese oxidation is the transport of manganese to the slag-metal interface. The activation energy of manganese oxidation is 63.4 kJ/mol. The mass transfer coefficient and the diffusion coefficient of manganese are 0.0226 cm/s and 7.0×10^–5 cm²/s respectively at 1600°C.