Kinetic Analysis Considering Particle Size Distribution on Ca Elution from Slags in CaO–SiO₂–MgO–Al₂O₃–Fe₂O₃ System

Abstract

The understanding of the behavior of alkali elution from slags is important for their effective recycling and utilization. In a previous study, it was reported that the addition of iron oxide to steel slags significantly inhibited alkali elution. A lower modified basicity, i.e., CaO/(SiO₂ + Fe₂O₃) ratio, indicates a lower alkali elution from the slags. In addition to the effect of Fe₂O₃ content, particle size distribution is an important parameter to determine the elution of Ca quantitatively.

In this study, a kinetic model considering particle size distribution is developed and applied to the results of a dissolution experiment using samples of a slag, which is designated as SlagF4, with different particle size distributions. In the new kinetic model, an effective surface area and the effectiveness of total surface area α are introduced, and a kinetic analysis is performed.

The rate constant k obtained is a fixed value for one sample type; k decreased with the increase in Fe₂O₃ content.

The values of α increased significantly with the increase in the total surface area S_T (i.e., a decrease in particle diameter) in different particle size distributions. It is discovered that α typically represents the Ca elution tendency. Additionally, the change in α is small with the change in the Fe₂O₃ content. It is demonstrated that the developed kinetic model is valid for the analysis of Ca elution for samples with different particle size distributions.