In this study, the decomposition conditions of limestone particles (0.25-0.50 mm) for CO2 capture in a steam dilution atmosphere (20-100% steam in CO2) were investigated by using a continuously operating fluidized bed reactor. The results show that the decomposition conversion of limestone increased with the steam dilution percentage in the CO2 supply gas. At a bed temperature of 920 degrees C, the conversions were 72% without steam dilution and 98% with 60% steam dilution. The conversion was 99% with 100% steam dilution at 850 degrees C of the bed temperature. Steam dilution can decrease not only the decomposition temperature of limestone, but also the residence time required for nearly complete decomposition of CaCO3. The hydration and carbonation reactivities of the CaO produced were also tested and the results show that both the reactivities increased with the steam dilution percentage for decomposing limestone. (C) 2009 Elsevier B.V. All rights reserved.