Development of a CaO-based CO2 sorbent with improved cyclic stability

The carbonation of CaO is an attractive method for removing CO2 from hot gas mixtures. However, regeneration and reuse of a CaO-based sorbent causes a gradual decline in absorption capacity, which ultimately limits the life of the material. Various methods have been proposed for increasing the life cycle performance of a CaO-based sorbent. Two of these methods were selected for further investigation. One method incorporates an “inert” material in the sorbent, while a second method stabilizes the sorbent through controlled sintering. Promising results were achieved with both methods when they were applied separately to a sorbent derived from a natural limestone. In one case MgO was finely dispersed within the sorbent, where it served as an “inert” material in the sense that it did not absorb CO2. A concentration of approximately 20 wt % appeared to be nearly optimal. In a second case the sorbent was stabilized by calcining the material at 1100 °C for 5 h. Although neither method produced a completely stable material, the stability of the sorbents was improved sufficiently so that by the end of a 1200-cycle test the absorption capacity of either of the treated sorbents was 45% greater than that of an untreated sorbent and the rate of decline was very small