Conversion efficiency of carbonate formation from steel slag via CO2 pressurization

This study explores the carbonation of Basic Oxygen Furnace (BOF) steel slag for CO2 sequestration, focusing on the effects of steel slag particle size, pressure, temperature, and liquid content on calcium carbonate (CaCO3) formation. The carbonation process was analyzed over varying reaction times (1, 2, 4, 8, and 24 hours) as well. The results showed that the smaller slag particles, due to their higher specific surface area, enhanced the CaCO3 production rate. While the increased reaction time tended to increase carbonation, the initial rapid uptake of reaction during the early stage was followed by the gradual convergence, attributed to the depletion of reactive sites. Increasing the CO2 pressure from 0.5 to 10MPa led to the higher reaction efficiency. Carbonation rates were lower at 55°C compared to 25°C, especially at the early stages, likely due to reduced CO2 solubility in water at higher temperature. The liquid-solid ratio (L/S) did not significantly affect the final carbonation rate after 24 hours, suggesting water availability was not an influencing factor. Additionally, the study employed Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA) to identify the mineralogy and precipitation patterns of CaCO3 formed at different conditions. This comprehensive analysis underscores the complex interplay of factors affecting BOF slag carbonation, providing insights that could optimize CO2 sequestration efficiency.