Phase evolution of cement raw meal in a high-CO2 atmosphere

This study investigates the effects of a high-CO2 atmosphere on phase evolution, burnability, and clinker mineral formation in cement raw meals using high-temperature X-ray diffraction (HT-XRD). The cement industry is a significant CO2 emitter, primarily from limestone decomposition and fuel combustion. Innovative solutions such as carbon capture and storage (CCS) are critical, with electrification and oxy-fuel combustion showing promise. Electrification using plasma technology, which employs CO2 as a carrier gas, offers a pathway to near-zero emissions. Four industrial raw meals from northern Europe were analyzed under conventional (20% CO2) and high-CO2 (95% CO2) conditions. Chemical composition, particle size distribution, and coarse fraction analyses preceded HT-XRD data collection across temperatures up to 1500 degrees C. High-CO2 conditions delayed calcite decomposition, reducing free-CaO availability and altering burnability. The timing of calcite decomposition relative to C2S formation suggests a reaction pathway in which free CaO, released from calcite, rapidly reacts with thermally activated SiO2 to form C2S. Additionally, spurrite decomposition released reactive CaO and C2S, enhancing C3S formation at 1300-1400 degrees C in spurrite-rich samples. Above 1400 degrees C, melt formation promoted further C3S development, leading to similar final levels in both tested atmospheres. These findings indicate that high-CO2 conditions significantly influence clinker phase evolution and reactivity. Practical implications include optimizing raw meal composition and kiln temperature profiles in electrified and oxy-fuel systems to enhance burnability while minimizing operational issues such as spurrite-induced kiln buildup. Future research should further explore industrial scalability and raw material adjustments to enhance CO2 efficiency during clinkerization.