A Compact Kinetic Model for Biomass Pyrolysis at Gasification Conditions

Computational fluid dynamics (CFD) tools are increasingly gaining importance to obtain detailed insight into biomass gasification. A major shortcoming of the current CFD tools to study biomass gasification is the lack of computationally affordable chemical kinetic models, which allows detailed predictions of the yield and composition of various gas and tar species in complex reactor configurations. In this work, a detailed mechanism is assembled from the literature and reduced to a compact model describing the gas-phase reactions of biomass gasification in the absence of oxygen. The reduction procedure uses a graph based method for unimportant kinetic pathways elimination and quasi-steady-state species selection. The resulting reduced model contains 39 gas species and 118 reactions and is validated against the detailed model and two experimental configurations: the pyrolysis of volatile species, such as levoglucosan, in a tubular reactor, and the fast pyrolysis of biomass particles in a drop tube reactor. The reduced model predicts the evolution of major gas products (e.g., CO, CO2, CH4, H-2) and various classes of tar (e.g., single-ring aromatics, oxygenated aromatics, PAHs) produced during biomass gasification. The capability of the reduced model to adequately capture the chemical process in a complex reactor geometry at an acceptable computational cost is demonstrated by employing it in a simulation of a pseudo two-dimensional laboratory-scale fluidized bed reactor.