Experimentally Derived Arrhenius Coefficients for the Reaction Modeling of Fast Pyrolysis

The search for fossil fuel alternatives has been one of increasing interest in recent years and one method which shows evidence of feasibility on a large scale is the production of bio-oil through the pyrolysis of biomass. In order to mathematically characterize biomass pyrolysis reactions for the purpose of process modeling, reaction descriptors in the form of Arrhenius coefficients are frequently utilized. Due to the complexity and inhomogeneity of biomass molecular structures, strictly analytically derived Arrhenius coefficients are not capable of predicting pyrolysis behaviors and outcomes. Typically thermogravimetric analysis (TGA) is employed as a method of extracting mass conversion data as a function of temperature from which bulk reaction descriptors following the form of Arrhenius reaction coefficients are derived. The preceding time and temperature history, however, will have a significant impact on the biomass conversion processes at each subsequent data point. This renders derived process predictors from TGA incapable of approximating fast pyrolysis reactions which have a markedly different time and temperature history than is seen utilizing TGA methods. Experimentally derived reaction descriptors of the Arrhenius form for the fast pyrolysis of biomass have been investigated utilizing a novel isothermal fast pyrolysis reactor. Multiple reaction durations and reaction temperatures for Pinus Taeda were tested resulting in measurements of biomass conversion. Reaction coefficients derived from the data are compared to coefficients derived utilizing TGA data and their predictions for mass conversion are contrasted.