Decarbonisation of cement industry: Calcium looping with white mud and limestone as CaO-based sorbents for industrial flue gas treatment

Abstract

This study investigates the potential of CaO-based sorbents from white mud and limestone for CO₂ capture in the Calcium-looping (CaL) process, employing both dry synthetic gas and real industrial flue gas (FG) from a cement plant (<0.3 % moisture). Exploring white mud as a CO₂ sorbent offers a novel way to valorise waste, aiding waste reduction. The CO₂ capture capacity was evaluated in a laboratory scale Fluidized Bed Reactor over ten carbonation-calcination cycles (calcination: 930 °C, 70 % CO₂; carbonation: 700 °C, 15 % CO₂). Sorbents carbonated with FG demonstrated improved performance and stability, emphasizing moisture's role. These conditions generally improved sorbent textural properties after cycling. Results also showed that higher CO₂ capture was associated with fresh sorbents having lower SiO₂ content (<0.73 wt. %), whereas higher SiO₂ content led to decreased performance. In conclusion, white mud offers potential for greener CO₂ capture. The research further examines the potential for reducing calcination temperature when steam is used in both calcination-carbonation stages. Adding 15 vol. % steam was found to improve CO₂ capture capacity at a lower calcination temperature (910 °C), achieving 0.29 g CO₂/g sorbent in the first cycle. Our preliminary approach revealed that using steam during both stages is promising at low calcination temperatures.