Model for diffusion coefficient estimation of calcium ions in CaO–Al₂O₃–SiO₂slags

Abstract

As a common component in metallurgical slag, CaO plays an important role in desulphurisation, dephosphorisation and absorption of non-metallic inclusions. In order to better understand the mechanism of the slag/metal reactions, the diffusion dynamics of calcium ions in CaO-Al 2 O 3 -SiO 2 slags were studied. It was found that there was almost a linear relation between the logarithms of pre-exponential factor and diffusion activation energy. By combining the relation between the diffusion activation energy and the optical basicity corrected in the CaO-Al 2 O 3 -SiO 2 slags, a simple model used to estimate the diffusion coefficient of calcium ion is proposed. The estimated values of the CaO-SiO 2 and CaO-Al 2 O 3 -SiO 2 systems agree well with the experiment data, with a mean deviation of 35?3 and 22?5% respectively.

Dissolution of CaO in SiO2-CaO-Al2O3 Slag in Si Production

“…Experimental research has found that the mass transfer in the slag is typically the ratedetermining step for the CaO dissolution in SiO 2 -CaO-Al 2 O 3 slag. A number of researchers have also deduced the diffusivity from dissolution rate data [3][4][5][6][7][8][9][10][11]. A short summary with the diffusion coefficients together with the respective slag composition and temperature is listed in Table 1.…”

“…Ren et al [11] developed a model for estimating the diffusion coefficient related to the structure of the slag instead of viscosity and electrical conductivity. The structure of the slag is often described by optical basicity, free oxygen, bridging oxygen, non-bridging oxygen and the ratio of non-bridging oxygen to tetrahedral cations.…”

“…The constants a, b, c and d were optimized by using experimental data from Goto et al [7] and Zhang and Chou [10]. In the model from Ren et al [11], there was an increasing function relationship between the logarithm of the pre-exponential factor and the diffusion activation energy calculated by optical basicity. With the increasing polymerization degree of molten slag, the diffusion coefficient of calcium ions decreases.…”