4 - Synthetic calcium oxide-based carbon dioxide sorbents for calcium looping processes

Abstract

One of the most promising approaches for the capture of CO2 from flue gases is the use of CaO-based CO2 sorbents. For CaO-based materials, the capture and release of CO2 follows the reversible reaction: CaO(s)+CO2(g)↔CaCO3. However, unmodified CaO derived via calcination of naturally occurring limestone shows a rapid decay of its CO2 uptake capacity with cycle number. Here, we review fundamental aspects of the carbonation and calcination reaction, putting particular emphasis on the morphological changes of CaO over multiple carbonation–calcination cycles. Subsequently, recent attempts to develop synthetic CaO-based CO2 sorbents, viz. unsupported CaO derived via the calcination of complex calcium precursors and CaO supported on a high Tammann temperature (temperature at which sintering starts) matrix, which substantially exceed the cyclic CO2 capture capacity of limestone, are presented.