Autothermal Sorption-Enhanced Steam Reforming of Renewable Syngas: Composition-Dependent Hydrogen Yield and Energy...

Producing renewable hydrogen from biomass is essential for the transition to low-carbon energy systems and sustainable fuel production. Biomass-derived syngas streams from biorefineries are a promising hydrogen source, but their compositional variability and high fractions of CO₂ and H₂ significantly affect hydrogen production performance. Sorption-enhanced steam reforming (SESR) combines steam reforming with in situ CO₂ capture using CaO-based sorbents, enhancing hydrogen production through process intensification. This work investigates autothermal SESR enabled by CO₂-rich feed compositions and heat integration to improve energy efficiency. An Aspen Plus equilibrium model was used to evaluate the effects of syngas composition and operating conditions (steam-to-carbon = 2.5-6.5, CaO/C = 1.5-2.5) on hydrogen production and energy performance at 600 °C and 10 bar. CO-rich feeds improve H₂ purity, CH₄ conversion, CO₂ capture efficiency, and cold gas efficiency (CGE) by promoting the water-gas shift reaction and methane reforming through reduced CO₂ partial pressure. In contrast, CH₄- and H₂-rich feeds decrease H₂ purity and methane conversion due to lower effective steam-to-methane ratios and equilibrium limitations. However, these compositions improve overall energy efficiency by reducing the external fuel required for sorbent regeneration. Increasing steam availability enhances performance up to a threshold beyond which Ca-(OH)₂ formation becomes significant, which strongly penalizes efficiency due to additional regeneration energy demand. Under optimal conditions, hydrogen purities up to 99.2 vol %, CO₂ capture efficiency of 98.8%, and a CGE of 81% are achieved. These results help define operating windows for autothermal SESR and support the design of flexible and energy-efficient hydrogen production systems.