Autothermal Reforming of Glycerol with Supercritical Water for Maximum Power through a Turbine Plus a Fuel Cell

An autothermal reforming of glycerol process using supercritical water was proposed to produce maximum power by means of a turbine, from the huge pressure energy of product gas just at the outlet of the reformer, and a proton exchange membrane (PEM) fuel cell, which is fed by a hydrogen-rich stream. The reformate gas is upgraded to hydrogen using serially two water gas shift reactors and a pressure swing adsorption unit. To achieve the energy self-sufficiency condition, all of the pressure swing adsorption (PSA) off-gas, which mainly consists of methane and non-recovered hydrogen, is used as fuel gas to provide a fraction of the thermal energy required by the overall process, and thus, the oxygen needed within the supercritical autothermal reformer is reduced. The system analysis was performed by simulation using AspenPlus, and simulation results are presented. Different reforming and preheating temperatures were taken, and the best values of both water/glycerol and oxygen/glycerol mole ratios to maximize power production were identified. Thus, by reforming and preheating at 800 degrees C and 240 atm, a specific power of 1.60 kW/kg of glycerol with exergy and energy efficiencies of 33.5 and 36.0%, respectively, was obtained. In addition, a comparison with the use of glycerol as a fuel in a combined Brayton-Rankine cycle showed a lower overall energy efficiency.