| A thermogravimetric analyzer (TGA) was used to obtain information on the pyrolysis and combustion behavior of crude oil (Neilburg) and derived asphaltenes, mixed with reservoir sand. Of all the SARA (saturates, aromatics, resins and asphaltenes) fractions, asphaltenes contribute the most to the formation of coke (fuel). Temperature-ramped as well as the isothermal pyrolysis experiments on whole oil and asphaltenes were analyzed to determine the temperature at which coke formation was maximized. Using custom written software, the results obtained were normalized to 1 mg of pure sample. Furthermore, isothermal combustion curves for coke derived from whole oil and asphaltenes were obtained to provide reliable data for calculating the kinetics of the reactions. The classical Arrhenius model was applied and the activation energy for the combustion of coke formed from pure asphaltenes and the whole oil were calculated. It was observed from the results that the activation energy for asphaltenes was 117.7 kJ/mol and for the whole oil, 129.5 kJ/mol indicating that they were close. From the experimental values, it was also found that the combustion of coke from asphaltenes showed a reaction order of 0.4 at 375°C, which gradually increased to 0.9 at 525°C. For whole oil, it was 0.5 at 375°C, which increased to 0.7 at 500°C. |
