A compartmental one‐dimensional model of a fluidized bed pyrolytic converter of biomass is presented. Reference conditions are those of non‐catalytic fast pyrolysis of biomass in a shallow fluidized bed with external regeneration of the bed material. The fate of biomass and of the resulting char has been modelled by considering elutriation of biomass and char particles, char attrition as well as bed drain/regeneration. The course of primary and secondary pyrolitic reactions is modelled according to a semi‐lumped reaction network using well‐established kinetic parameters taken from the literature. A specific focus of the present study is the role of the heterogeneous volatile–char secondary reactions, whose rate has been modelled by borrowing a kinetic expression from the neighbouring area of tar adsorption/decomposition over char. The results of computations highlight the relevance of heterogeneous volatile–char secondary reactions and of the closely associated control of char loading in the bed. The sensitivity of the reactor performance to char elutriation and attrition, to proper management of bed drain/regeneration, and to control of gas phase backmixing is demonstrated. Model results provide useful guidelines for optimal design and control of fluidized bed pyrolyzers and pinpoint future research priorities.

A model of non-catalytic fast fluidized bed pyrolysis of biomass has been developed with the aim of investigating the relevance of secondary heterogeneous reactions between primary products of biomass decomposition and the char accumulated in the bed. The fate of biomass and the extent of biomass and char holdup in the pyrolyzer have been modeled by considering entrainment and elutriation of biomass and char particles, char attrition, as well as bed drain/regeneration. The kinetics of primary and secondary pyrolitic reactions is modeled according to a semi-lumped reaction network using kinetic parameters selected among published correlations. The rate of heterogeneous volatile–char secondary reactions has been modeled borrowing a kinetic expression from the neighboring area of tar adsorption/decomposition over char during biomass gasification. Model computations are helpful to assess the role of heterogeneous vapor–char secondary reactions. The sensitivity of the pyrolyzer performance on char loading in the bed as a result of combined char entrainment, elutriation, attrition, and bed drain/regeneration, the extent of gas-phase backmixing, the process temperature, the gas superficial velocity and residence time, and the particle size is demonstrated and discussed. Model results provide useful guidelines and pinpoint future research priorities for optimal design and control of fluidized bed pyrolyzers.

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