PREDICTING REACTIVITY AND CONVERSION PROFILE OF AGRO-INDUSTRIAL RESIDUES IN STEAM GASIFICATION PROCESSES: A KINETIC APPROACH

The aim of this work is to predict the reactivity and conversion profiles of the steam-char gasification step of residual biomasses that are typical of the Mediterranean area. In order to simulate the conversion profiles of chars in steam atmosphere, kinetic constants and reaction models were correlated with the main catalytic and inhibiting elements. The chars were obtained from ctrus peel, grape pomace, reed (Arundo Donax), and residues from 2nd generation bioethanol production. The study was carried out by means of isothermal thermogravimetric experiments of the selected biomass chars in the temperature range from 650°C to 825°C in 50% (v/v) steam atmosphere (N2 as balance gas). By indicating as Inorganic Catalytic Ratio, ICR = (Ca+K)/Si the ratio between the main inorganic elements with catalytic and inhibiting effects, it was found that samples with ICR > 1 showed a so called sigmoidal conversion, which can be described by classical Avrami type models. The chars with ICR < 1, showed a decelerating profile of conversion, described by n-order models. The computed char conversions were in good agreement to the experimental data.