A fast pyrolysis of biomass in a rectangular bubbling fluidized bed were simulated using the multiphase particle in-cell (MP-PIC) based framework. A three-dimensional reactive gas - solid CFD simulation results were compared to the lab-scale (1 kg/hr) experimental data. To consider pyrolysis reaction with gas-solid flow two-stage, semiglobal kinetics was incorporated. The simulation results of this investigation show good agreement with the experimentally observed yield distribution. The influences of operating conditions (reaction temperature, superficial gas velocity, sand particle inventory) and reactor configuration (biomass feeding location, gas distributor configuration) on the products yield were analyzed and discussed. Overall, this study provides important guidelines for possible reactor intensification and optimization.