Bench-scale and modeling study of sulfur capture by limestone in typical CO₂ concentrations and temperatures of fluidized-bed air and oxy-fuel combustion

In this study, the influence of CO₂ on sulfur capture efficiency was studied during fluidized-bed desulfurization by experiments and modeling. During calcination–sulfation and direct sulfation, the effect was examined with one limestone type. A time-dependent multilayer particle model was used for analyzing the experimental results. The model determines the magnitude of the reactions and the diffusion as a function of the radius and time. In high temperatures (∼1200 K), CO₂ increased the conversion degree during calcination–sulfation. In direct sulfation, the effect of CO₂ was opposite; lower conversion was obtained when the CO₂ concentration was increased. When the CO₂ concentration was increased in low temperatures (∼1100 K) (close to the calcination curve), CO₂ retarded the conversion strongly. The detected differences between the results are explained with the development of the Thiele number, conversion curve, and conversion profile during the reactions.