The effect of adsorbent characteristics on the performance of a continuous sorption-enhanced steam methane reforming process

Abstract

The steam methane reforming (SMR) process for hydrogen production with in situ CO 2 capture on adsorbent particles pneumatically conveyed through a monolithic catalytic reactor and subsequently regenerated ex situ, was considered. A mathematical model has been formulated, based on differential mass and energy balances in the reactor and the regenerator, Langmuir isotherm for CO 2 sorption equilibrium, the linear driving force approximation for sorption kinetics, and literature values for the kinetics of the three main SMR reactions. The effect of the adsorbent characteristics—the maximum CO 2 capacity and the sorption kinetics—on the overall process performance in terms of methane conversion and CO 2 separation has been systematically investigated in a parametric study. The main conclusions of the study are that: (i) conversion enhancement and CO 2 recovery show a strongly non-linear dependence on both sorption capacity and kinetics; (ii) comparable conversion enhancement and CO 2 recovery can be achieved by means of both lithium zirconite-like (high capacity, slow kinetics) and hydrotalcite-like (low capacity, fast kinetics) adsorbents; (iii) if an ideal adsorbent possessing hydrotalcite-like sorption kinetics and zirconite-like capacity were developed, the conversion enhancement factor could be more than doubled and a nearly 100% CO 2 recovery could be achieved under otherwise identical conditions.