THERMAL DEHYDRATION OF CALCIUM HYDROXIDE .2. SURFACE-AREA EVOLUTION

The evolution of the specific surface area associated with the thermal decomposition of calcium hydroxide has been studied experimentally and described by kinetic models utilizing two different solids: commercial calcium hydroxide (S0? 8.3 m2-1) and calcium hydroxide reagent (S0?18.7 m2g-1). The surface area was observed to vary linearly with the fraction decomposed during the dehydration period. Sintering phenomena have been experimentally measured by treating calcium oxide samples (S0? 46 m2.g-1), obtained after dehydration of calcium hydroxide under constant conditions, at temperatures in the range 500-900 °C for periods of time up to 24 h. A previously developed model, German and Munir (1976), fits the experimental results well if the surface area decreases to less than 55% of the initial value. An empirical kinetic model, where the surface area is linearly related to the heating time, correlates the experimental data, when ΔS/S055%. Simulated curves using the obtained kinetic models and parameters, for the specific surface during dehydration and sintering, agree well within the experimental results. © 1990, American Chemical Society. All rights reserved.