Structure and dynamic viscosity of CaO–SiO₂ and CaO–SiO₂–B₂O₃ model slag systems

Correlation dependencies between the dynamic viscosity of slag and its structural parameters were studied to determine an optimal basicity of silicon smelting slag under the addition of boron oxide to eliminate slagging of the bottom of ore-smelting furnaces. Experimental studies were conducted on CaO–SiO₂ and CaO– SiO₂–B2O₃ model slags obtained at 1600°С. Raman spectroscopic analysis was carried out using a Horiba JobinYvon HR800UV analyzer (France). Theoretical calculations of slag viscosity were performed using Urbain and Mills models. During the experiments, the key structural parameters of slag systems varied within the following limits: the experimental Raman spectrum deconvolution function from 1.41 to 2.45 and optical basicity from 0.58 to 0.68. The obtained experimental and theoretical data were related by mathematical dependencies. It was found that the dynamic viscosity of slag can be promptly determined by Raman spectroscopy on the basis of mathematical models. The dependence obtained shows that slag viscosity decreases upon an increase in the number of bridging oxygen atoms in the silicate anion structure. Notably, this decrease in slag viscosity is observed up to the value of the experimental Raman spectrum deconvolution function of ~1.55-1.60 or slag optical basicity of 0.60–0.62. When B₂O₃ is added, the viscosity undergoes a further decrease. In practice, for CaO–SiO₂ slag systems, the use of boroncontaining flux as a liquefying agent is reasonable at CaO/SiO₂ = 0.61–0.63 while maintaining the content of B₂O₃ in the slag at a level of 1%. The two models (classical and modified) proposed by Urbain were established to be more suitable for theoretical calculation of viscosity in CaO–SiO₂ and CaO–SiO₂–B2O₃ systems. Mills’ model is not suitable for these purposes, since the correlation coefficients in the corresponding mathematical model are not sufficiently large. Further research in this direction is required in order to establish appropriate dependencies of slag viscosity on its structural parameters at different temperatures.

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