Steam-Enhanced Calcium Looping Cycles with Calcium Aluminate Pellets Doped with Bromides

Abstract

This study explores the effect of calcium bromide (CaBr2) doping of lime-based sorbents in the presence of steam during calcination/carbonation cycles. Two sorbents were tested: natural limestone (Cadomin, Canada) and a synthetic sorbent (pellets) prepared from Cadomin limestone with addition of calcium aluminate cement. The mixture of calcined limestone and cement was pelletized in a mechanical granulator that uses spray water as the part of the pelletization process. Both the original limestone and the prepared pellets were impregnated with a dilute CaBr2 solution to achieve a Ca/Br mole ratio of 500:1. The CO2 carrying activities of the sorbents were tested during calcination/carbonation cycles in a thermogravimetric analysis (TGA) apparatus. Realistic calcination conditions during the reaction cycles were employed: 900 °C with a CO2 sweep gas. Multicycle tests were carried out with steam 15% and without steam present in the carbonation gas stream (20% CO2, 15% steam or 0% steam, N2 balance in both cas...