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

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 degrees C, 70 % CO2; carbonation: 700 degrees 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 degrees 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.