The effect of C content in MgO-C on dissolution behavior in CaO-SiO2-Al2O3 slag

This study was conducted to observe the dissolution behavior of MgO-C in CaO-SiO2-Al2O3 ternary slag using the Single Hot Thermocouple Technique (SHTT). The composition of the slag was CaO (41.5 wt%), SiO2 (41.5 wt%), Al2O3 (17 wt%), and MgO-C (0, 5, 10, 18 wt%). When the slag was completely melted, MgO-C particles were added and the dissolution behavior was observed in real time. Before the main experiment, the weight of MgO-C and slag was set by designing a stability diagram for the short circuit problem of the thermocouple (TC) caused by the bubble reaction. Comparing the dissolution behavior of MgO and MgO-C revealed that the dissolution time of MgO was shorter than that of MgO-C in which bubbles occurred. When the C content of MgO-C was 10 wt% or more, particle fragmentation was observed, and the dissolution time decreased as the C content increased. Bubbles were formed in the sample to which C was added. The main bubble reaction was C(s) + SiO2(l) = CO(g) + SiO(g) based on thermodynamic analysis and weight loss measurements where the total partial pressure was P-T=P-CO+P-SiO=0.18 atm. In addition, the kinetic behavior of weight loss as a function of time strongly depended on the C content, and thus, it depended on the effective C surface area.