KINETIC-ANALYSIS OF NONISOTHERMAL CALCINATION TG CURVES OF NATURAL TURKISH DOLOMITES

Calcination kinetics of six dolomite samples originating from different parts of Turkey were investigated by using the non-isothermal thermogravimetry technique. Calcination TG curves of samples were obtained under two different atmospheres of (1) pure nitrogen and (2) a mixture consisting of 15 vol.% CO2 and 85 vol.% dry air, by using a constant heating rate of 10 min-1. Kinetic analysis of the curves was achieved by applying four different methods of calculation; also, 14 different model equations of possible solid-state rate controlling mechanisms were considered. Arrhenius parameters E and A and the model function f(alpha) that best describes the reaction mechanism were evaluated for the decomposition reactions of both MgCO3 and CaCO3 components of samples. A computer program in BASIC which enables regression analysis to be carried out was used to obtain kinetic results from experimental non-isothermal TG data. It was observed that besides differences in the chemical composition of samples, gaseous atmosphere and the method of calculation influenced the results obtained.