Oxidation kinetic evaluation of the low temperature oxidized products of Tahe heavy oil characterized by the distributed activation energy model

Abstract

© 2019 Elsevier B.V. In view of the significance of low temperature oxidation (LTO) for in-situ combustion (ISC) of heavy crude oil and to provide further data for Tahe ISC numerical simulation, this research aimed to investigate the non-isothermal oxidation behavior of heavy oil after static LTO reactions. Thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques were used to characterize oxidation behavior, and distributed activation energy method (DAEM) was used to calculate kinetic parameters. The results showed that the non-isothermal oxidation process of static LTO oxidized oil was the result of the interaction between residue and coke, and coke can significantly reduce the activation energy of oxidized oil. Only one HTO region was identified for the coke from DTG/DSC curves, and it had the lowest activation energy (114.57 kJ/mol) and the highest heat enthalpy (24.3 kJ/g), indicating high oxidative activity with maximum heat release potential. A satisfactory corresponding relation between DTG and DSC curves was presented for all samples in FD and HTO regions, which indicated that the sequential reaction mechanisms, fuel deposition and combustion, were undergone. In LTO region, there was a temperature difference between the peaks of the mass loss and heat flow, indicating that the LTO process was more complex with a multi-step control mechanism should be considered to analyze and simulate the LTO stage.