Document Type : Research Paper
School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran
In this study, thirteen surface samples were selected and investigated to characterize the oil shale thermal decomposition process from the Middle Jurassic Sargelu Formation in Lorestan province (Southwest Iran). The oil shale samples, for the first time, were studied using Differential Scanning Calorimetry (DSC) and the non-isothermal Thermogravimetric (TG-DTG) analysis with heating rates of 5, 10, and 15 °C/min. Thermo-oxidative decomposition of the Sargelu oil shale was occurred in three steps: (1) the thermo-oxidation of bitumen (according to the heating rate ranging from 210 °C to 401 °C), (2) the thermo-oxidation of the kerogen (between 365 and 560 °C), and (3) finally, the decomposition of calcite mineral (between 541°C and 815 °C). The thermal experiments show that the peak temperatures and reaction region intervals increased to greater temperatures by an increase in the heating rate. The activation energy parameter analyzed through the oil shale thermo-oxidative kinetics was evaluated using the ASTM E-698, Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) approaches. The mean activation energy calculated during low-temperature thermo-oxidative of the Sargelu oil shale is 127 KJ/mol. Compared to the Early Cretaceous Garau oil shale with the mean activation energy of 183 KJ/mol from the same locality (Shekarifard et al., in press), the Sargelu oil shale has lower activation energy. Eventually, kinetics analysis confirmed the occurrence of kerogen with (very) fast reaction rate in the Sargelu oil shale.