(127f) Ultra-Stable Calcium Oxide Absorbents for High Temperature CO2 Capture

Calcium oxide-based materials are attractive regenerable absorbents for separating CO2 from hot gas streams because of their high reactivity, high CO2 capacity, and low material cost. Especially, their high carbonation temperature (600oC to 700oC) makes it possible to recover and use the high quality heat released during CO2 capture, which cam largely increase the overall process efficiency. However, the performance of all reported CaO-based absorbents deteriorates as the number of carbonation-decarbonation cycles increases. Rapid loss of CO2 capacity over many carbonation/decarbonation cycles is always observed due to severe absorbent sintering. Recently, we have found that this sintering effect can be effectively mitigated by properly mixing with a modest amount of small particles of inert additives. A new class of CaO-based absorbents with much improved durability and CO2 reactivity were prepared by physical mixing of Ca(CH3COO)2 with MgAl2O4 spinel nanoparticles followed by high temperature calcination. A CaO-MgAl2O4 (32 wt.% spinel content) material provides 34 wt % CO2 capacity after 65 carbonation-decarbonation cycles (650oC and 850oC, respectively), corresponding to 63 % CaO utilization. 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 first cycle to less than 5 wt.% for the 50th cycle.