The reactivity of calcium oxide towards carbon dioxide and its use for energy storage

Abstract By using calcium carbonate powder of particle size ∼ 10 nm (and therefore of high surface area) it has been shown that the reaction CaCO 3 ⇄ CaO + CO 2 can be made almost wholly reversible. A reactivity of 93% was achieved, (i.e. 93% of the calcium oxide reacted with carbon dioxide) and this was maintained for 30 24‐h decomposition‐back reaction cycles at 629 °C with no detectable decrease. This material has an energy storage capacity of 200 Wh/lb, but only about 1 kWh/ft. 3 When this calcium carbonate was pressed, however, to increase its bulk density (from 0.1 to ∼ 1 g/ml) there was a large decrease in its surface area and a smaller decrease in its reactivity on undergoing a few decomposition and back reaction cycles. Scaling up of the sample size from 20 mg to 10 g only had a small (× 3) effect on the rates of decomposition and back reaction.