Slag and refractory compatibility in the CONSTEEL EAF
MetadataShow full item record
This project is in collaboration with Celsa Armeringsstål AS facilities in Mo i Rana, consisting of a steel mill, with a continuous charging EAF (CONSTEEL Electric Arc Furnace), and a combined rolling mill for reinforcing bar and wire rod. The production is purely scrap based and is Norway s largest recycling company. To ensure a stable and efficient process of scrap melting in an EAF, a good slag practice is needed. The refractory of the EAF consists mainly of MgO, due to this MgO is added as dolomite to decrease the chemical wear. A slag with too much MgO will however be unfavorable for the foaming and thus covering the arcs. A chemical balance where the slag is able to trap the CO/CO2-gas generated by the reduction of FeO in the slag is therefore required. However, experience at Celsa Armeringsstål AS has shown that the established theory used by EAF operators describing slag optimization might not be fully applicable to the CONSTEEL technology.Therefore, the main aim of this thesis is to investigate the MgO saturation in synthetic slag (composition varying in basicity and FeO content) samples, focusing on chemical composition and its effect on refractory wear.MgO saturation in the synthetic slags were first studied using the FactSage software, a thermodynamic program consisting of a series of modules that access and manipulate thermodynamic databases. The data gained by FactSage was further used to decide the range to be studied in the experiments. Experiments were performed by adding MgO pellets to the synthetic slag, then using different analytical method to define MgO saturation in each slag. MgO-C refractory wear in the synthetic slag at 1600°C was also studied by utilizing factsage and preforming experiments of static corrosion test. Based on the results obtained from the thermodynamic calculation and experimental data, several conclusions have been reached according to the problems this work was set to achieve. These conclusions can be summarized as following: MgO solubility increases with increasing temperature for all slags studied. MgO solubility decreases with increasing basicity for FeO 20-40wt%. Increasing FeO wt% decreases the effect basicity has on MgO solubility. Static corrosion test shows that wear on MgO-C increases with decreasing basicity and increasing FeO wt% in the slag.