Determination of non-isothermal reduction kinetics of gördes laterite ore-tunçbi̇lek lignite coal mixture by thermal gravimetry

In this study, fine laterite samples from Manisa Gördes mine were calcined, and mixed with dried and fine Tunçbilek lignite particles in molar stoichiometric ratio (87% laterite and 13% lignite). Afterwards, the mixtures were heated from ambient temperature to 1000 ºC under N2 flow at different heating rates; 5, 10, 15, 25, and 40 ºC/min in a thernogravimetric analyser. All experiments were repeated for the same amount of lignite keeping all other parameters the same. Using the weight loss values of both lignite and mixture samples, reduction degrees of the metallic oxides in the ore samples were calculated. Due to the low concentration of the lignite in the mixtures, the highest reduction degree was around 29%. The obtained data was analyzed by non-isothermal kinetic methods and the mean activation energy (Ea) for 0 to 0.18 conversion range of the reduction was determined as 107.97 kJ/mole, 51.87 kj/mole, and 63.67 kj/mole via Friedman (FR), Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods, respectively. On the other hand, Coats-Redfern (CR) method revealed that the initial stage of the reduction of calcined Gördes laterite by Tunçbilek lignite between 0 and 0.29 conversion range progressed under phase boundary chemical reaction control with Ea of 54.04 kJ/mole.