An energy and exergy analysis of the supercritical water reforming of glycerol for power production

As a continuation of a previous work, a conceptual design is proposed for reforming glycerol using supercritical water to produce maximum electrical power in an energy self-sufficient system. The scheme of the process is simulated after discussing some routes to achieve the aim. The selected way takes advantage of the huge pressure energy of reformate products just at the outlet of the reforming process. The expanded product gas is used as a fuel gas to provide the thermal energy required by the reforming process. The evaluation of the thermodynamic performance of the process is carried out by an energy and exergy analysis. As relevant outputs measurements of the process performance, the net work and exergetic efficiencies as well as the mole fraction and molar flow-rates of hydrogen obtained. Glycerol feed concentration in aqueous solution at which no external heat source is needed was obtained, both for pure and pretreated crude glycerol, at 800 °C and 240 atm. The effect of the main operating parameters has been investigated by sensitivity analysis to identify optimal conditions that maximize power production. In the exergy analysis, the thermodynamic efficiencies used for the overall process and for its individual units are suitably discussed. The computation has been made with the aid of AspenPlus™, using the predictive Soave-Redlich-Kwong equation of state as thermodynamic method in the simulation of the supercritical region. The next study in this series of glycerol reforming using SCW will aim to maximize hydrogen production, including the syngas purification, to generate electricity via fuel cells.