Gasification kinetics of chars from diverse residues under suitable conditions for the Sorption Enhanced Gasification process

Abstract

Gasification kinetics for six chars from residual origin have been determined in a relatively low temperature range, low CO2 and high H2O partial pressures, typical from Sorption Enhanced Gasification (SEG) processes. In general, models based on the Random Pore Model (RPM) are the best fitting experimental results, but ash composition (in terms of alkali and alkaline earth metals) was crucial for the selection of the reaction model to be applied. Char conversion from biogenic waste with ash content higher than 30 % wt. was modelled with RPM model, but reaction rate for chars with the highest K/Si ratio was better described with modified versions of the RPM capable of predicting maximum reaction rates at high char conversion. For chars with similar ash content and composition, textural properties determined the pre-exponential factor and the activation energy for the gasification reaction (with both CO2 and H2O), while identical fitting parameters for the semi-empirical model were capable of predicting char conversion with time.