Thermodynamic Phase Equilibrium Composition Determination of Ethanol Steam Reforming by Direct Minimization of Gibbs Free Energy Using Peng-Robinson Property Method

Abstract

Determination of appropriate process parameters for ethanol conversion to obtain maximum hydrogen yield and zero net carbon deposition via ethanol steam reforming was studied. Thermodynamic equilibrium analysis of ethanol steam reforming was carried out by direct minimization of Gibbs free energy method using Aspen Plus (V8.8). Equilibrium compositions of each species were analysed for temperatures ranging from 873 to 1173K, steam-ethanol molar ratio of 2:1 -6:1 and pressure at 1atm.The performance of the reformer is expressed in terms of conversion and yield[1][2]. The highest ethanol conversion was observed to be 66.7% with respect to feed ratio of 2 for the considered temperatures (see Figure1), due to thermodynamic limitation and preference of CO and H2 production at low input [4]. The maximum hydrogen yield(84.8%) was observed at temperature of 1073K relating to feed molar ratio 2:1 and at pressure of 1atm (shown in Figure 2), which implies that CO and H2 are mainly produced at low input [3]. The reforming reactions operated at high temperature enhance the formation of hydrogen, being an endothermic reaction and the reduction of carbon (IV) oxide shifted the equilibrium in favour of hydrogen. The prediction of the simulation is significant, since the considered process parameters lead to maximum hydrogen yield and carbon formation minimization, which is yardstick for the commercialization of hydrogen production from ethanol steam reforming. for fuel cells application.