MgAl ₂ O ₄ Spinel-Stabilized Calcium Oxide Absorbents with Improved Durability for High-Temperature CO ₂ 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 CO 2 capture from coal power plants. The major limitation of these absorbents is that the carbonation and decarbonation reactions of CaO and CaCO 3 are far from complete or reversible. Rapid loss of CO 2 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 MgAl 2 O 4 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 MgAl 2 O 4 spinel particles followed by high-temperature calcination. CaO−MgAl 2 O 4 (32 wt % spinel content) material provides 34 wt % CO 2 capacity after 65 carbonation−decarbonation cycles (650 and 850 °C, respectively), corresponding to 63% CaO use. Under the same test conditions, the CO 2 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.