Thermoanalysis and reaction kinetics of heavy oil combustion

Abstract

The present study deals with fingerprinting the oxidation behavior of a Brazilian crude (12° API) oil. It focuses on the determination of reaction kinetic parameters through classical thermal analysis techniques such as thermogravimetry (TG), differential thermal analysis (DTG) and scanning calorimetry (DSC). The required experimental data are collected from oil and oil–sand samples. The reaction data are treated following distinct conventional and isoconversional non-isothermal models, using integral and differential approaches based on Arrhenius’ model. The thermoanalytical study is successful in identifying three oxidation temperature ranges: the low-temperature (LTO) range, a transition zone, and the high-temperature (HTO) range. TG and DSC analyses show that the highest variation of mass and the highest level of energy generation occur at the HTO range. At the high end of the LTO range, a mass transfer resistance (skin effect) was evident. Values of activation energy obtained for oil samples are 103 kJ mol−1 for LTO and 278 kJ mol−1 for HTO oxidation reactions by the most straightforward method used—the unity model. By all kinetic models, HTO’s values are higher than those for LTO, observation also valid for the results of oil–sand samples. Results also evidence that the presence of sand contributes to the so-called skin effect.