SIMULATION AND ENERGY ANALYSIS OF A REFORMER FOR HYDROGEN PRODUCTION BY AUTOTHERMAL REFORMING OF METHANOL

Abstract

Methanol is considered to be an attractive fuel for hydrogen production as it is renewable source of energy and produces hydrogen with relatively low CO content. In the present study, a one dimensional steady state non isothermal model was developed to simulate fixed bed reactor to carry out autothermal reforming of methanol. The model equations were solved simultaneously by using ODE solver tool in MATLAB R2008a. The effect of different parameters like S:C ratio in feed and temperatures on methanol conversion, H2 yield, and mole % of CO, CO2, H2O, and CH3OH were examined. The molar flow rates of different species and output temperatures in the fixed bed reactor were calculated. Methanol conversion of 99.99% was obtained at a temperature of 523 K (250°C) and S:C ratio of 1 in feed. The exergy analysis was carried out to examine the energy utilization of inlet feed stream in the reformer during oxidative steam reforming of methanol. The exergy efficiency was found to be 89.9% at 523 K and S:C ratio of unity. The thermal efficiency at 523 K and S:C ratio of unity was 94.7% which was 4.8% higher than the exergy efficiency. The thermal efficiency was reduced at higher S:C ratio in the feed. The exergy destruction varied inversely with temperature and directly with S:C ratio. The low value of exergy efficiency indicated small thermodynamic irreversibilities in the reformer. The variation in hydrogen efficiency with S:C ratio was not significant while its variation with temperature was positive and quite significant. Thus, autothermal reforming of methanol at 523 K (250°C) and S:C ratio of unity utilizes sufficient amount of input energy in the form of useful work.