MgAl2O4 Spinel-Stabilized Calcium Oxide Absorbents with Improved Durability for High-Temperature CO2 Capture

With efficient energy recovery, calcium-oxide-based absorbents that operate at elevated temperatures have an advantage over absorbents that operate at lower temperatures for CO2 capture from coal power plants. The major limitation of these absorbents is that the carbonation and decarbonation reactions of CaO and CaCO3 are far from complete or reversible. Rapid loss of CO2 capacity over many carbonation/decarbonation cycles is always observed because of severe absorbent sintering. We have found that this sintering effect can be effectively mitigated by properly mixing calcium oxide precursors with small rod-like MgAl2O4 spinel nanoparticles. A new class of CaO-based absorbents with much improved high-temperature durability was developed by wet physical mixing of calcium acetate with nano MgAl2O4 spinel particles followed by high-temperature calcination. CaO−MgAl2O4 (32 wt % spinel content) material provides 34 wt % CO2 capacity after 65 carbonation−decarbonation cycles (650 and 850 °C, respectively), corresponding to 63% CaO use. Under the same test conditions, the CO2 capacity of natural dolomite (35 wt % MgO and 65 wt % CaO) decreases rapidly from 25 wt % for the 1st cycle to less than 5 wt % for the 50th cycle.