Accelerated weathering of construction-grade limestone for CO2 absorption

Abstract

Accelerated weathering of limestone (AWL) process efficiently captures CO₂ from point source emissions. However, despite achieving an outstanding capture efficiency of 73.51 %, lab-grade (LG) limestone with 99.90 % CaCO₃ as an absorbent is costly ($2757.70/t), making commercialization of AWL impractical. This work delves into the viability of utilizing construction-grade (CG) limestone (93.26% purity) for the AWL process facilitated by potable water in an absorption tower for post-combustion capture. The result shows that CG limestone achieves comparable CO₂ capture efficiency of 8.0–74.68% and bicarbonate (Ca(HCO₃)₂) concentration of 0.63–3.10 mM compared with LG limestone. However, LG limestone has 0.29 mol CO₂/mol CaCO₃ higher CO₂ absorption capacity and a faster absorption rate than CG limestone, indicating a somewhat better CO₂ capture performance. Nevertheless, CG limestone offered a more cost-effective alternative, with a $2735.24 lower cost per ton of CaCO₃ and a $2651.63 per ton CO₂ lower CO₂ capturing cost at the highest carbon capture efficiency (HCCE) condition compared to LG limestone. The kinetic analysis shows that the forward reactions in the AWL process are significantly faster at elevated CO₂ concentration, with the mass transfer coefficient affirming that CO₂ dissolves faster than CaCO₃, in line with prior research. Thus, this work validates that CG limestone-based AWL achieves comparable CO₂ capture performance to that of LG limestone, offering a cost-efficient alternative. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.