Computational Fluid Dynamics Modeling of Steam Co-Gasification of Biochar and Waste Mixed Plastic in Downdraft Fixed Bed Reactor

This research investigates steam co-gasification of biochar and waste mixed plastic through computational fluid dynamics. The overall goal of this research is to maximize H₂ compound. A 3-dimensional fixed bed downdraft reactor was modeled using commercial ANSYS Fluent software. In this model, only steam was introduced alongside the particle for the reaction. To track the movement of biochar particles, discrete phase modeling (DPM) was used. From the species transport model, finite-rate/eddy-dissipation was used for the reaction kinetics. Seven thermochemical conversion reactions were employed, consisting of both homogeneous and heterogeneous types. The simulation was conducted under steady-state conditions, and the k-ε model was used for turbulence. The impact of temperature and steam-to-feedstock (S/F) ratio on syngas composition such as H₂, CO, CO₂, CH4 was examined. The temperatures were changed from 800ºC to 1000ºC. The maximum hydrogen production was attained with S/F of 4.88 at 900ºC. As the S/F ratio escalated from 1 to 4.88, the mole fraction of hydrogen and carbon dioxide increased, and carbon monoxide decreased. At a constant S/F ratio, carbon monoxide concentration escalated at higher temperatures. The addition of plastic to the process resulted in a significantly reduced carbon dioxide compound in syngas.