Optimization of power and hydrogen production from glycerol by supercritical water reforming

A process design is proposed and simulated for reforming glycerol using supercritical water aimed to produce maximum power and hydrogen in an energy self-sufficient system. The selected route takes advantage of the huge pressure energy of product gas just at the outlet of the reformer converting that into power by a turbine. The expanded product gas is conditioned by two water gas shift reactors and a pressure swing adsorption unit, so a hydrogen-rich gas stream is sent to a proton exchange membrane fuel cell to be converted into electrical energy and the pressure swing adsorption off-gas stream is used as fuel gas to provide the thermal energy required by the reforming process. The evaluation of the global efficiency of the process is carried out by energy and exergy analysis. Required glycerol feed concentration in aqueous solution was obtained for a self-sufficient process, both for pure and pretreated crude glycerol, at reforming temperatures from 600 to 1000 degrees C and 240 atm. Thus, reforming and preheating at 800 degrees C and 240 atm, it was obtained a power of 1592 kW per ton/h of glycerol, with exergy and energy efficiencies of 33.8% and 35.8%, respectively. (C) 2012 Elsevier B.V. All rights reserved.