CFD Modeling of Gas Phase Tar Chemistry in a Fluidized-Bed Biomass Gasifier

A limitation of biomass gasification in a fluidized-bed reactor is the high level of tars in the product gas, causing fouling and hazardous waste. A possible approach would be to directly optimize the gasifier design and operating conditions to the biomass properties for minimal tar production. However, it requires a better understanding of the detailed chemical and physical processes occurring simultaneously in the reactor. CFD offers a unique opportunity to incorporate fundamental results, for example from detailed chemical modeling, into a larger scale framework, allowing to gain some global insight on tar reduction methods. In this work, a detailed chemical mechanism is assembled, that accounts for biomass devolatilization, decomposition of primary products, and formation of aromatic rings and PAH. The chemical model is then integrated into CFD simulations of turbulent fluidized-bed reactors to study the effect of mixing processes and inhomogeneity on the amount and composition of tar at the exit of the gasifier.