Thermodynamic Simulation and Sensitivity Analysis of the Steam Reforming of Methane Using Gibbs Free Energy Minimisation

Steam reforming of methane (SRM) supplies about half of the world’s hydrogen, but a high heat demand and carbon-forming side reactions that deactivate Ni catalysts limit its performance. HSC Chemistry 6 was used to compare the spontaneity of SRM with methane decomposition, water–gas shift, the Boudouard reaction, CO and CO2 methanation, dry reforming and partial oxidation between 100 and 1000 °C, and to determine by Gibbs free energy minimisation how the CH4/H2O feed ratio (1:1, 2:1, 1:2) and pressure (1–5 bar) shift the equilibrium composition. SRM is non-spontaneous at 25 °C and becomes spontaneous above about 620 °C. Methane decomposition becomes spontaneous earlier, at about 545 °C, and is the main thermodynamic carbon threat. A methane-rich feed deposits carbon equal to 47–49% of the methane fed above 640 °C, an equimolar feed forms carbon between about 440 and 840 °C, and a steam-rich feed is carbon-free and reaches 99% conversion at 820 °C. Raising the pressure from 1 to 5 bar lowers methane conversion (76% to 45% at 685 °C) and hydrogen yield, but suppresses carbon formation. The results support steam-rich, low-pressure, high-temperature operation.