Evolution of biomass char features and their role in the reactivity during steam gasification in a conical spouted bed reactor

A study was carried out on the effect the evolution of the porous structure and metal content have on the gasification rate during char gasification in a conical spouted bed reactor. Partially gasified samples at different temperatures (800-900 degrees C range) were collected at various conversion levels and characterized by different techniques (N-2 adsorption-desorption, ultimate/proximate analysis and X-ray Fluorescence). At 900 degrees C there is a fast development of the porous structure, attaining the highest BET specific surface area (S-BET) (633 m(2) g(-1)) at low conversion. Char reactivity profiles revealed that the development of the porous structure influenced the reaction rate mainly at early stages, whereas the increase in the gasification rate for conversions higher than 60% (especially at 900 degrees C) was attributed to the catalytic effect of Ca, K and Fe (the main metals in the ashes).