THE EFFECTS OF STEAM AND CARBON-DIOXIDE ON CALCITE DECOMPOSITION USING DYNAMIC X-RAY-DIFFRACTION

The effects of steam (H2O) and carbon dioxide (CO2) on the rates of ca lcite decomposition have been studied using dynamic X-ray diffraction (DXRD). Because the DXRD technique allows for considerably better cont rol of heat and mass transfer complications, intrinsic decomposition r ates are obtained for temperatures between 440-560 degrees C and up to H2O and CO2 pressures of 0.2135 and 0.00087 atm, respectively. It is shown that the observed enhancement effect of steam is related to its adsorptive properties which are faster and more significant than CO2 a dsorption. This, in turn, leads to the hypothesis of a quantitative La ngmuir-Hinshelwood model which is totally compatible with the kinetic data. Separate adsorption experiments show that the effect of steam pr essure is limited due to adsorption saturation capacity and the model is used to predict the steam pressure required to produce 95% of the m aximum effect of steam as a function of temperature.