Green route for biomethane and hydrogen production via integration of biogas upgrading using pressure swing adsorption and steam-methane reforming process
Ammar Ali, Mohd Roslee Othman, Hasan Sh. Majdi, Zuchra Helwani
Abstract
Biogas is a cornerstone within a clean and sustainable energy portfolio, while hydrogen production from biogas is a key enabler for methane conversion and carbon dioxide valorization for greenhouse gases emissions mitigation. In this work, pressure swing adsorption (PSA) configuration of two vessels-four adsorption beds connected in series was tested for upgrading low-grade biogas (50% CH 4 and 50% CO 2 ). To resolve CH 4 spillage issue, steam-methane reforming (SMR) plant was proposed as a green route for converting CH 4 and portion of CO 2 in the waste stream of PSA system into hydrogen. The integrated system (PSA-SMR) was performed on two stages i.e., PSA runs were conducted experimentally in lab while SMR system was simulated using Aspen Hysys software under operating conditions from a real plant. Response surface methodology was applied into Design Expert software to optimize the effects of system pressure, CH 4 concentration, and biogas/steam flowrate ratio on H 2 , CO 2 , H 2 O, and CO molar fractions in the product. The results revealed that four adsorption beds in serial configuration successfully recorded ultrapure CH 4 of 99.9% and recovery of 84.9% along with average CO 2 content of 60% in the waste stream. For SMR system, produced syngas comprised of 42.2% H 2 , 28.46% CO 2 , 13.84% N 2 , 8.88% H 2 O, and 6.66% CO with 100% conversion of the CH 4 and about 52.56% conversion of the CO 2 . The optimum conditions that achieved the highest H 2 content of 51% from SMR were system pressure below 32 bar, methane content in feed stream ≥61%, and biogas/steam ratio in the range of 0.41–0.66 to record H 2 .