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–SiO 2 –Al 2 O 3 ternary slag using the Single Hot Thermocouple Technique (SHTT). The composition of the slag was CaO (41.5 wt%), SiO 2 (41.5 wt%), Al 2 O 3 (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) + SiO 2 (l) = CO(g) + SiO(g) based on thermodynamic analysis and weight loss measurements where the total partial pressure was P T = P C O + P S i O = 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.