Optimizing hydrogen production and efficiency in biomass gasification through advanced CFD modeling

Gasification is a thermochemical process that converts biomass into biochar, bio-oil, and syngas. This study applies Computational Fluid Dynamics (CFD) to predict Cold Gas Efficiency (CGE) and hydrogen yield (yH₂), integrating a pyrolysis submodel and an average intrinsic reactivity approach for solid–gas reactions to assess the influence of temperature on gas composition and reaction kinetics. A two-dimensional downdraft gasifier model was developed to simulate species transport and reaction mechanisms under four experimental treatments: gasification with air (B), with CaCO₃ as a catalyst (BC), with steam addition (BS), and with both steam and CaCO₃ (BCS). Model validation demonstrated that CFD accurately captured the effects observed experimentally, predicting syngas composition with a global error of 7.71 %. The highest CGE achieved was 61.6 %, and the maximum yH₂ reached 308 ml H₂/g biomass under the BCS condition, where the combination of steam and CaCO₃ enhanced hydrogen production by promoting tar reforming and CO₂ capture. The results confirm that steam and CaCO₃ improve cold gas efficiency and hydrogen yield, aligning with experimental observations. This study highlights CFD as a reliable tool for predicting biomass gasification performance, particularly for hydrogen-rich syngas production.