Kinetics of the Reaction of Iron Blast Furnace Slag/Hydrated Lime Sorbents with SO2 at Low Temperatures: Effects of the Presence of CO2, O2, and NOx

The effects of the presence of CO 2, O 2, and NO x in the flue gas on the kinetics of the sulfation of blast furnace slag/hydrated lime sorbents at low temperatures were studied using a differential fixed-bed reactor. When O 2 and NO x were not present simultaneously, the reaction kinetics was about the same as that under the gas mixtures containing SO 2, H 2 O, and N 2 only, being affected mainly by the relative humidity. The sulfation of sorbents can be described by the surface coverage model and the model equations derived for the latter case. When both O 2 and NO x were present, the sulfation of sorbents was greatly enhanced, forming a great amount of sulfate in addition to sulfite. The surface coverage model is still valid in this case, but the model equations obtained show a more marked effect of relative humidity and negligible effects of SO 2 concentration and temperature on the reaction. The effect of sorbent composition on the reaction kinetics was entirely represented by the effects of the initial specific surface area ( S g0 ) and the Ca molar content ( M −1 ) of sorbent. The initial conversion rate of sorbent increased linearly with increasing S g0, and the ultimate conversion increased linearly with increasing S g0 M −1 . The model equations obtained in this work are applicable to describe the kinetics of the sulfation of the sorbents in the low-temperature dry and semidry flue gas desulfurization processes either with an upstream NO x removal unit or without.