Análise de operabilidade da produção de gás de síntese a partir do processo sequencial de reforma a seco e reforma a vapor do biogás

Abstract

This dissertation presents a mathematical modeling-based integrated analysis of synthesis gas (syngas) production from biogas through the sequential combination of dry reforming of methane (DRM) and steam reforming of methane (SRM) processes. The adopted methodology involved the development of a thermodynamic model based on the minimization of Gibbs free energy, accounting for non-idealities via the fugacity coefficient of each species in the mixture, capable of predicting the equilibrium composition of the involved species, and its validation using experimental data from the literature. The study assessed the impact of operational variables such as temperature (in the range of 600–1500 K), CH4/CO2 feed molar ratio (1.5 to 4), and water vapor molar flow rate (4 to 16 kmol·h−1) on process outputs such as syngas composition, H2/CO molar ratio, and carbon formation. The best results were obtained at temperatures of 1000 K and 1150 K in the DRM (R1) and SRM (R2) reactors, respectively, CH4/CO2 feed ratio ≥ 1.5, and a steam flow rate of 8 kmol·h−1, corresponding to a steam-to-carbon ratio (S/C) of 1.33. These conditions enabled the achievement of an H2/CO ratio ≥ 2.0, high reactant conversion, and low carbon formation, under operating conditions comparable to those used in industrial reformers. Furthermore, the operability index (OI) was determined as an optimization tool, identifying safe and efficient operational regions of the process. The OI reached a value of 81.64%, indicating a good overlap between achievable and desirable output sets. The results demonstrate that the reforming process employing sequential reactors is a viable and promising alternative for the conversion of the main components of biogas into synthesis gas, offering high flexibility and selectivity - especially when combined with operability analysis methods - thus contributing to the development of sustainable syngas production technologies from renewable waste sources.