Equilibrium Calculation of Gaseous Reactive Systems with Simultaneous Species Adsorption

This work focuses on the calculation of chemical equilibrium in a gaseous reactive system with simultaneous single or multiple species adsorption under isothermal and isobaric conditions. Two different algorithms are developed, following the minimization of Gibbs free energy and the concept of equilibrium constant, respectively. In either case, the problem formulation is converted to a set of nonlinear algebraic equations that are solved using the Newton−Raphson scheme. An example of steam reforming of ethanol with simultaneous CO2 adsorption is used to illustrate the proposed approaches. It is shown that at T = 500 °C and P = 5 bar, the CO2 removal ratio should exceed 40% to achieve a decent enhancement in hydrogen production and purity. An integrated process that combines the endothermic reforming and the exothermic combustion of CH4 from the off-gas supplemented with simultaneous CO2 adsorption in the reforming process yields a theoretical maximum overall conversion rate of 86.3% (the corresponding H2 purity out of the reformer is 89.4% on a wet basis, or 96.2% on a dry basis) with little or no external heat supply. The analysis in this work is potentially useful in the design and optimization of adsorption-enhanced reforming reactors for hydrogen generation and other applicable reactive systems.