High temperature SO2 retention by CaO

SO2 retention with CaO at high temperature (1073 K), both in the absence and in the presence of O2, has been studied. For this purpose, CaO samples coming from eight different limestones and commercial CaCO3 have been used. Both limestone and CaO obtained from these samples were widely characterized. The ‘classical’ textural parameters of limestone or CaO (BET surface, pore volume, etc.) do not correlate with the SO2 retention degree at 1073 K. However Temperature Programmed Reaction experiments (TPR) in a thermobalance may help to select the best limestone (CaO) to be used as SO2 sorbent at 1073 K; in fact there seems to be a relation between the TPR type, the CaO dispersion (determined by CO2 chemisorption at 573 K), and the retention degree reached. Consequently, CO2 chemisorption at 573 K could be used to predict limestone behaviour with respect to SO2 retention at 1073 K.