This paper develops a simple, yet practical, steady-state kinetic reactor model for lime-enhanced biomass steam gasification in a dual fluidized bed reactor, one of the most promising technologies for sustainable production of hydrogen. The focus is on kinetic modeling of the bubbling fluidized bed gasifier, accounting for in situ sorbent carbonation, while assuming complete char combustion and complete sorbent calcination in the circulating fluidized bed riser. The kinetic model for the gasifier includes a generic two-step reaction kinetic mechanism for primary and secondary biomass pyrolysis, with phenol as a model tar compound and a reaction network for tar thermal cracking and reforming, major homogeneous and heterogeneous gasification reactions, and a first-order kinetic model, sufficient to simulate the carbonation of highly cycled sorbent particles at steady state. An ideal reactor model is used for the gasifier, assuming perfectly mixed solids and plug flow of the gas phase. Predictions of the product gas distribution are in good agreement with literature experimental data on the effect of Ca-looping rate, gasifier temperature and steam-to-biomass ratio for Absorption Enhanced Reforming (AER) of biomass in both 20 kWth and 200 kWth dual fluidized bed systems operating at steady-state. This predictive model is useful for optimizing design and operation of dual fluidized bed biomass gasifiers with lime-based CO2 capture.

Keywords