Kinetic model for desulphurization at low temperatures using hydrated sorbent

The sulphation reaction of hydrated silica fume-Ca(OH)(2) sorbents were inv estigated and modelled. These experiments were conducted in a thermogravime tric analyzer under isothermal conditions and in a humidified gaseous atmos phere consisting of 5 vol% O-2, 10 vol% CO2, 0.5 vol% SO2 and the balance o f nitrogen. The effect of the relative humidity on the reaction rate was de termined by sulfating of hydrated sorbents in the gaseous atmospheres which have three different relative humidities: 25%, 55% and 90%. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (h ydrated sorbent/SO2) reaction mechanism. The experimental results were foun d to be correlated successfully by this model. It was determined that chemi cal reaction is partly rate limiting especially at the beginning of sulphat ion, diffusion through the calcium sulphite hemihydrate product layer gener ally controls the reaction rate. (C) 1999 Elsevier Science B.V. All rights reserved.