Research on characteristics and modelling estimation of molten BF slag viscosity in the process of slag waste heat recovery

The object of this study was to explore the effects of basicity (CaO/SiO₂ ratio), MgO and Al₂O₃ on viscosity and melting temperature of molten slag in the process of coal gasification with blast furnace (BF) slag as heat carrier to recover the waste heat. The results showed that the viscosity and melting temperature of BF slag decreased first and then increased with CaO/SiO₂ ratio increasing, and the suitable CaO/SiO₂ ratio was 1.10–1.20. Both viscosity and melting temperature increased with the increasing of MgO and Al₂O₃ in the slag, which should be lower than 8.22 and 11.00%, respectively. What is more, the viscosity estimation model for molten BF slag was established according to the Urbain model and experimental data of slag viscosity. In the model, the activation energy was calculated using slag compositions based on the redefine of material types in the slag, and the temperature was described by the Weymann–Frenkel equation. The viscosity of BF slag system estimated by proposed viscosity estimation model (modified Urbain model) fitted well with the experimental data and the mean deviation was about 17.98%.