Experimental determination of CO₂ mineralization depth of slag minerals at CO₂ concentrations available in iron and steelmaking flue gases

We report the diffusion coefficient relevant to CO2 mineralization using minerals commonly encountered in ironmaking and steelmaking slag. Diffusion coefficients were gained from CO2 mineralization achieved under passive conditions consistent with processes that are likely to maintain net CO2 emission reduction. In other words, no chemical, thermal, or mechanical enhancement was applied. Tests were performed at 30 ◦C with molar CO2 concentrations of 0.04%, 5%, and 20%. We applied the diffusion coefficients using the shrinking core model with a modification to account for the full particle size distribution of a sample and the fractal surface roughness. Results indicate that CO2 mineralization efficacy is highly variable among minerals common to slag; thus, the slow kinetics and low conversion common to slag-based CO2 mineralization is likely due in part to blockage of reactive species by unreactive species. Further, the modified shrinking core model matches early phase CO2 mineralization rates where the traditional models fail. Analysis of slag-based CO2 mineralization methods should thus account for the specific mineralogy, particle size distribution, and micromorphology of tested slag.