Comparison between model-based and non-isothermal model-free computational procedures for prediction of conversion-time curves of calcium carbonate decomposition

The model-based and non-isothermal model-free procedures have been applied for prediction of conversion-time curves of calcium carbonate decomposition. In this purpose, the thermogravimetric (TG) curves corresponding to decomposition of CaCO3 have been recorded in nitrogen flow in non-isothermal conditions at constant heating rates of 2.5; 5.0; 7.5; 10.0; 12.5 and 14.9 K min(-1), and in other temperature programs that exhibit the following final isothermal steps: 650 degrees C; 660 degrees C; 670 C and 700 degrees C. To apply model-based procedure, the most probable kinetic schemes and corresponding kinetic parameters have been determined by using the non-isothermal data, and the isoconversional and multivariate nonlinear regression (Multivar-NLR) methods. By comparing the experimental and predicted conversion-time curves that exhibit a final isothermal step, it as been obtained that the most probable kinetic scheme consists a reversible reaction of CaCO3 decomposition followed by diffusion of carbon dioxide. The non-isothermal model free prediction procedure has been also used for assessment of conversion-time curves that exhibit a final isothermal step. Both model-based procedure and non-isothermal model-free procedure lead to satisfactory agreements between experimental and calculated conversion curves corresponding to temperature programs that exhibit a final isothermal step, but the curves predicted by a non-isothermal model free procedure have a large deviation from the experimental ones than those predicted by model-based procedure.