Dissolution behavior of SiO₂ in the molten blast furnace slags

Abstract

The kinetics of SiO2 dissolving in the molten blast furnace slags at 1743‐1803 K was studied using a High Temperature Confocal Scanning Laser Microscopy (HT‐CSLM), and then the effects of temperature, MgO and Al2O3 on the SiO2 dissolution were clarified in this study. The experiment results showed that the dissolution process is controlled by the solute diffusion in the slag. The SiO2 dissolution rate could be accelerated by increasing the temperature. Moreover, the SiO2 dissolution rate is the fastest in the slag with 11.0 pct MgO when the MgO varies between 7.0 and 13.0 pct. The SiO2 dissolution rate is the fastest in the slag with 18.0 pct Al2O3 when the Al2O3 varies between 14.0 and 20.0 pct. The effects of temperature, MgO and Al2O3 on the SiO2 dissolution rate could be indicated by a simple expression (csat−cb)/η that a larger of (csat−cb)/η is associated with the faster SiO2 dissolution rate, where (csat−cb) is the difference between the concentration of SiO2 in the saturated slag and in the bulk of slag, and η is the slag viscosity.

Dissolution behavior of silica in molten CaO–SiO2–Fe2O3–MgO–MnO slag

“…Table 4 summarizes the dissolution rate of some oxides in different slag systems. The dissolution rate of fused silica in the molten BOF slag in the present work is in the range of 2.63–7.81×10 −4 cm·s −1 , which is close to the previous works 31,33,34 . By comparison, the dissolution rate of Al 2 O 3 and MgO is varied from 3.22×10 −6 ∼1.025×10 −4 cm·s −1 and 5.8×10 −6 ∼1.2×10 −5 cm·s −1 , respectively 15,20,21,27,28 .…”

“…34 The present result is consistent with the previous work. [31][32][33][34] This can be attributed to the missing of intermediate compounds on the join of the SiO 2 -slag at the temperature interval between 1773 and 1873 K. 46 Furthermore, the phase relations between slag and SiO 2 were determined by FactSage simulation, as shown in Figure 9. The starting point is the phase composition of initial slags at the equilibrium state and the ending point is pure silica.…”

“…Fewer works were conducted on the dissolution kinetics mechanism of SiO 2 . [29][30][31][32][33][34] Cooper et al 29,30 studied the dissolution of fused silica in 20 wt.% Al 2 O 3 -40 wt.% CaO-40 wt.% SiO 2 slag and revealed that the dissolution rate was controlled by the transport in the molten silicate. Feichtinger et al 31 in situ observed the dissolution of amorphous SiO 2 particles in the CaO-Al 2 O 3 -SiO 2 slag.…”

“…They concluded that the driving force of SiO 2 dissolution during the sintering process was the concentration difference between the boundary layer and the slag. As for molten blast furnace slag (CaO-SiO 2 -MgO-Al 2 O 3 system), Tian et al 33 considered that the dissolution rate of SiO 2 was controlled by diffusion. Recently, the dissolution kinetics of SiO 2 in the photovoltaic cutting waste slag system was studied by Zhang et al, 34 who found that the SiO 2 dissolution was also controlled by diffusion.…”

Dissolution Mechanism of Modifying Agent in Fibrotic Process of Steel Slag

“…To study the dissolution mechanism of lime in the slag, Valdez et al 17) and Yan et al 18) suggested that solute dissolution was controlled by mass transfer in the slag, while others argued that it was controlled by mass transfer in the boundary layer of molten slag. [19][20][21][22][23][24] Meanwhile, Guo et al 25) implied that the dissolution mechanism would change from reaction control to liquid film diffusion control for CaO, mass transfer in the boundary layer of molten slag for MgO, and mass transfer in the liquid slag for Al 2 O 3 .…”