Characterization of a Marl-Type Cement Raw Meal as CO₂ Sorbent for Calcium Looping

The use of cement raw meals as sorbent precursors for CO₂ capture can reinforce the synergies between the cement production process and calcium looping CO₂ capture technology. In this work, we measure the CO₂-carrying capacity of different calcined samples of a particular marl, which were obtained under very different calcination conditions and setups (a thermogravimetric analyzer, a drop tube furnace, and an industrial calciner). We find that the reactivity toward CO₂ of these calcined materials displays a strong sensitivity to the calcination conditions, in particular to calcination time. A pronounced competition between the belite (Ca₂SiO₄) formation reaction and the formation of free CaO needed for CO₂ capture is detected. As the calcination of the raw meal approaches flash conditions (i.e., >90% calcination conversion in less than 10 s), the belite formation is shown to be minimized, leading to sorbents with CO₂-carrying capacities of approximately 0.4 mol CO₂/mol CaO.