Performance Enhancement of Calcium Oxide Sorbents for Cyclic CO2 Capture—A Review

While calcium oxide has been identified to be the best candidate for capturing CO2 at high temperature, it suffers a well-known problem of loss-in-capacity; that is, its capacity for carbon capture decays dramatically during cyclic carbonation/calcination processes. Recently, extensive research work has been conducted on the enhancement of the cyclic performance of calcium oxide through either improving the performance of natural minerals, such as water/steam hydration and pretreatment or modification of calcium oxide sorbents by some techniques such as doping and synthesis. This work summarizes the state-of-the-art research in the literature aiming to identify potential solutions to the loss-in-capacity problem. It is found that hydration during or after calcination is effective in recovering the capacity of natural minerals and mixing can produce highly effective synthetic sorbents. Periodic hydration of synthetic sorbents could be a good strategy to overcome the technical issues associated with loss-in-capacity while meeting the requirements of the physical properties of sorbents in many potential applications.