Kinetic Modelling of Biomass Pyrolysis Processes

Biomass pyrolysis kinetics, coupled with the description of transport phenomena, produce advanced computational tools for the design and optimization (product yield and quality) of chemical reactors applied for the conversion process. Though kinetic analysis is generally based on standard thermogravimetric (TG) systems, the reliability of both the experimental data and the modeling may raise significant concern. The main difficulties consist in separating the effects of chemistry and transport phenomena, so as to establish a kinetic control, and the occurrence of primary and secondary reactions. The analysis is further complicated by the different contents and nature of the biomass macro-components and the catalytic action of the inorganics. For the estimation of the kinetic constants, TG curves, measured under different thermal conditions, are interpreted by means of different approaches including: model-fitting methods (one-stage pyrolysis mechanisms and multi-component devolatilization mechanisms), isoconversional (model-free) methods, and distributed activation energy models (DAEM). However, even in the case of biomass macro-components and standard feedstocks (e.g., wood) large variations are often reported on the estimated activation energies.