Wood pyrolysis consisting of water evaporation, consecutive, and parallel reactions was modeled through a multiple gas-solid reaction scheme. Effective kinetic parameters were determined through the model and compared to the results of a conventional differential method where the results differed substantially. The behavior of global wood conversion is compared to the experimental results. System parameters and variables, transport coefficients, and thermophysical proper ties are determined transiently. The millimeter sized pellets were found to have substantial gradients within. The heating rate of thermogravimetric analysis equipment is also considered in the model. The rate expressions were developed based on molar solid concentrations in the wood fibers. For the simulation grain (pore or fiber), pellet and reactor spaces of different magnitudes were considered. The effective quantities were DeltaE(1) = 255.7 kJ/mol, k(10) = 8.5 x 10(18) s(-1), DeltaE(3) = 40.7 kJ/mol, and k(30) = 4 x 10(6) s(-1).