Flue-gas desulfurization at medium temperatures. Kinetic model validation from thermogravimetric data

A thermogravimetric technique was used in the kinetic study of SO2 reaction with Ca(OH)(2) in the medium temperature range (300-400 degrees C) in order to compare results of different reaction systems. Two kinds of sample-holders were used: when a cylindrical sample-holder is used, the initial sulfation rate is mass-transfer limited; this resistance can be neglected using a specially designed 'net' sample-holder. From these experiments a strong decrease in the reaction rate was observed, ending with the deactivation of the sorbent at calcium utilization much lower than 1. The experimental 'conversion versus time' curves were compared with the simulations of the exponential kinetic model previously developed for the medium temperature desulfurization reaction in an integral sand-bed reactor: r(s)=ky(1-x(t))exp{-gamma(0)/RT exp(D/T)x(t)}. This model allows a good description of the thermogravimetric sulfation data. (C) 1998 Elsevier Science Ltd. All rights reserved.