Thermodynamic analysis of hydrogen production via hydrothermal gasification of hexadecane

This work reports the equilibrium behaviour of the hydrothermal gasification of hexadecane, a heavy saturate model compound, under non-oxidative isothermal and oxidative adiabatic conditions, using the Peng–Robinson equation of state and the direct minimisation of Gibbs free energy employed within the Aspen HYSYS. This modelling enabled establishing both the limits and optimum conditions at which the hydrogen molar yield may be theoretically maximised. The effects of parameters including the reactor isothermal temperature, pressure, water to carbon ratio, and oxygen to carbon ratio on the molar yields of produced gaseous species were analysed. The model has been validated by comparing its results with different reported modelling and experimental data under identical conditions which resulted in a good agreement. The results reported in this work show the potential of achieving economic yields of hydrogen and syngas from liquid hydrocarbons under downhole hydrothermal conditions.

► The conditions at which the hydrogen yield is maximise, were established.
► The optimum feed concentration was found to be 30 wt.%.
► H2 yield is thermodynamically maximised under high temperatures and low pressures.
► Oxygen injection reduced the starting reaction temperature and improved the syngas ratio.