Effect of MnO on Crystallization Behavior and Rheological Characteristics of Blast Furnace Slag during Gas Quenching into Beads

Abstract

The preparation of glass microbeads by gas quenching of blast furnace slag is an effective way to achieve efficient recovery and resource utilization of the residual heat from blast furnace slag. However, due to the high viscosity and easy crystallization of blast furnace slag, there are problems such as low bead formation rate, opaque glass microbeads, and poor chemical stability. MnO tempering agent was developed, and the influence of MnO on the crystallization behavior and rheological properties of the tempered slag was analyzed. The evolution law of the crystallization phase of the tempered slag was clarified, and a viscosity-crystallization coupling control method conducive to the bead formation of blast furnace slag was proposed. The results show that during the isothermal process, when the MnO content in the tempered slag is in the range of 0.17–12.24%, with the increase of its content, the initial crystallization temperature and the amount of crystal precipitation gradually decrease, effectively inhibiting the precipitation of crystals. However, when the MnO content exceeds 12.24%, the excessive MnO increases the activity of the easily precipitated phase, and the initial crystallization temperature increases instead. Therefore, when the MnO content in the tempered slag is 12.24%, the crystallization ability is the weakest, and the glass phase content is the highest. In the continuous cooling process, when the MnO content in the tempered slag is 12.24% and the cooling rate exceeds 3°C/s, the tempered slag completely solidifies into a glassy state.