CFD analysis of hydrothermal conversion of heavy oil in continuous flow reactor

•A new CFD model is developed for hydrothermal conversion of n-hexadecane.•True kinetic data are determined taking into account the radial effects.•The model is validated using existing experimental data.•The reaction is satisfactorily described by the first order rate law.•Reducing the reactor diameter may be important to maximise feedstock conversion.

CFD analysis is an important technique for reactor modelling and optimisation. In this work, we present a new CFD model used to determine true kinetic data of hydrothermal conversion of a heavy oil model compound, hexadecane, in a continuous flow reactor. Based on our previously reported experimental data, this model takes into account the radial effects occurring from the laminar flow conditions which enables producing modified Arrhenius plots from which true kinetic data are be obtained. Furthermore, the determined rate constants were used to validate the model through prediction of conversion in comparison with experimental data under identical conditions. The developed model shows good agreement with experimental data under isothermal conditions, while discrepancies in conversion profile arise under non-isothermal conditions which were found to be dependent on temperature assumptions. The reaction rate profile was investigated at different residence times for the different reaction regimes. The reactor was found to be nearly isothermal with the largest temperature gradient between the inlet and wall temperatures occurring at a distance 0-0.05 m in the z direction. The effects of reactor parameters including temperature and flow properties may be integrated into this model to predict the effects of various operating parameters and to optimise the design and behaviour of our reactor model. Our analysis shows that reducing the reactor diameter may be important to maximise feedstock conversion, and reaction rates, at lower temperatures.

Graphical abstractDownload high-res image (128KB)Download full-size imageCFD plot for the variation of n-hexadecane concentration along reactor surface at 595 °C, 13.89 s, and 220 bar.