High-Temperature CO₂ Uptake and Mechanical Strength Enhancement of the Calcium Aluminate Cement-Bound Carbide Slag Pellets

Abstract

Ca-rich solid waste, carbide slag, was adopted to prepare the CaO-based sorbent for CO2 uptake at elevated temperature. To alleviate the elutriation issue of CaO-based sorbent from the calcium looping system, the granulation of carbide slag was conducted via an extrusion-spheronization method. Calcium aluminate cement possessing excellent refractory property was selected as the binder. A range of cement-bound carbide slag pellets were prepared with the active CaO content varying from 25 to 70 wt %. The incorporation of calcium aluminate cement significantly decreases the CO2 capture capacities of the carbide slag pellets due to the irreversible consumption of active CaO by the silicates or aluminates within the cement. However, the average compression strengths of the fresh (3.29–9.82 MPa) and calcined (0.47–2.46 MPa) cement-bound carbide slag pellets gradually increase with the increase of cement addition. Additionally, the addition of rice husk can improve the CO2 capture performance of the cement-bound carbide slag pellets during the fast CO2 capture stage because of the generation of in stiu pores and cavities within the sorbent pellets. Although the cyclic CO2 capture performance of the cement-bound carbide slag pellets degrades under oxy-fuel calcination condition, to some extent, the low-cost and easily scaled-up preparation route may offsets the increased CO2 avoid cost because of the loss-in-capacity.