PNNL

Abstract

With efficient energy recovery, CaO-based high temperature absorbents have great advantages over other absorbents that operate at low temperatures for CO2 capture from coal power plants. The major limitation of this technique 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 due to severe absorbent sintering. We have found that this sintering effect can be effectively mitigated by properly mixing with small spinel particles. A new class of CaO-based absorbents with much improved high temperature durability was developed by wet physical mixing of Ca(CH3COO)2 with small MgAl2O4 spinel particles followed by high temperature calcination. With 10 wt % MgAl2O4 content, a CaO-MgAl2O4 mixture gives 50 wt % CO2 capacity after 100 carbonation-decarbonation cycles at 758 oC, corresponding to 72 % CaO utilization. Without MgAl2O4 addition, under the same test conditions, the CO2 capacity of pure CaO obtained from the same source decreases rapidly from 61 wt % for the first cycle down to 23 wt % for the 50th cycle, and further down to 18 wt % for the 100th cycle.