The kinetic rate of SO₂ sorption by CaO

Abstract

Abstract The intrinsic rate constant for the rate of reaction of SO 2 with porous CaO in an excess of O 2 to form CaSO 4 has been determined from SO 2 sorption data on a wide range of particle diameters (1 μm‐ 1mm), SO 2 partial pressures (60 Pa to 5 kPa), and temperatures (973‐ 1,478 K). An intrinsic SO 2 reaction order of unity has been validated through current fixed‐bed experiments in the 60 to 300 Pa SO 2 partial pressure range, while fluidized‐bed data were used to validate the reaction order from 500 Pa to 5 kPa SO 2 partial pressure. The absolute value of the rate constant and the activation energy was derived from data on small (1 μm) particles, which approach the limit of kinetic control. While analysis of this data base does minimize the role of intraparticle diffusion through the porous sorbent particle, the filling of the small pores by the product deposits and the associated loss of internal surface area is critical to the data reduction. It is believed that the intrinsic rate constant is known to the accuracy to which the reactivity and the BET surface area may be measured.