Analysis of Process Parameters and Particle Characteristics During Biomass Fast Pyrolysis: Effect on Biomass Conversion and Main Product Yields

A computational model of anisotropic biomass particle pyrolysis was developed to evaluate the influence of particle properties and operating conditions during fast pyrolysis. The model integrates multicomponent CRECK kinetics with intraparticle heat and mass transfer. Simulations were performed at reactor temperatures between 400 and 700 °C and convective heat transfer coefficients from 50 to 1500 W·m−2·K−1, representing conditions from slow to fast pyrolysis. Results showed that particle size and biomass composition strongly affect conversion time and product distribution, while aspect ratio becomes significant for larger particles. Increasing particle diameter from 3 to 8 mm more than doubled conversion times and increased char yield from approximately 16% to 23%. Lignin-rich biomass such as palm shell generated higher char yields and lower volatile production than cellulose-rich feedstocks such as oak or sugarcane bagasse. Higher reactor temperatures and heating rates reduced conversion times by up to 75%, with moderate effects on product yields. Analysis of Biot and pyrolysis numbers indicated that millimeter-scale particles operate in a transition regime where conduction, convection, and chemical kinetics occur on similar timescales. Therefore, accurate reactor design models must simultaneously consider coupled transport and reaction phenomena.