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

This study investigates the effects of a high-CO 2 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 CO 2 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 CO 2 as a carrier gas, offers a pathway to near-zero emissions. Four industrial raw meals from northern Europe were analyzed under conventional (20% CO 2 ) and high-CO 2 (95% CO 2 ) conditions. Chemical composition, particle size distribution, and coarse fraction analyses preceded HT-XRD data collection across temperatures up to 1500 °C. High-CO 2 conditions delayed calcite decomposition, reducing free-CaO availability and altering burnability. The timing of calcite decomposition relative to C 2 S formation suggests a reaction pathway in which free CaO, released from calcite, rapidly reacts with thermally activated SiO 2 to form C 2 S. Additionally, spurrite decomposition released reactive CaO and C 2 S, enhancing C 3 S formation at 1300–1400 °C in spurrite-rich samples. Above 1400 °C, melt formation promoted further C 3 S development, leading to similar final levels in both tested atmospheres. These findings indicate that high-CO 2 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 CO 2 efficiency during clinkerization. • High CO 2 delays calcite decomposition, affecting burnability and clinker formation. • Spurrite decomposes to reactive C 2 S and CaO, increasing C 3 S at lower temperatures. • Melt formation above 1400 °C equalizes C 3 S levels across high and conventional CO 2 . • High CO 2 atmospheres require optimized raw meal and burnability for efficiency.