HIGH-TEMPERATURE KINETICS OF FINE BIOMASS CHAR PARTICLES IN AIR AND CO_2

摘要

Knowledge of reliable chemical kinetics of char always plays significant roles in the modelling, designand optimization of processes during biofuel thermochemical conversions.The determination of reaction kinetics ofchar in the high-temperature range still highly depends on the extrapolation of results from kinetic data determined atlower temperatures due to mass and heat transfer limitations. In this work an aerosol-based method was used toinvestigate the reactivity of singly-distributed char particles with aerodynamic diameters between 0.5-10 μm. Theconversion of char particles in the reactor at varying temperatures and residence time was determined by comparingthe particle size distributions before and after passing the reactor, using an aerodynamic particle sizer (APS)spectrometer. The results of char particles reacted with air, CO_2 and steam indicate that the aerosol-based method canbe used to determine reaction kinetics of char particles in the high temperature range where reaction is controlled bydiffusion limitation if using conventional thermogravimetric analysis (TGA). By combining the aerosol-based methodand conventional TGA, the oxidation and gasification kinetic parameters of biomass char can be derived in thetemperature range of 350-800℃, and 800-1200℃ respectively. The aerosol-based method shows the potential of onlinemeasuring the char reactivity.