Mass transfer limitation in thermogravimetry of biomass gasification

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Nowak B, Karlstrom O, Backman P, Brink A, Zevenhoven M, Voglsam S, Winter F, Hupa M
Publisher: SPRINGER
Publication year: 2013
Journal: Journal of Thermal Analysis and Calorimetry
Journal acronym: J THERM ANAL CALORIM
Volume number: 111
Issue number: 1
Start page: 183
End page: 192
Number of pages: 10
ISSN: 1388-6150


Abstract

In order to determine the intrinsic reactivity behavior from thermogravimetry studies, the experimental conditions should be such that the reactions are not mass transfer limited. Biomass char usually has a higher reactivity than coal chars. Therefore, mass transfer limitations may be more problematic when studying biomass char reactivity. Chemical reaction kinetics and mass transfer processes present in thermogravimetry are used for modeling the overall reaction rate for spruce bark CO2 gasification. Thermogravimetric experiments are carried out between 700 and 900 A degrees C, and the CO2 concentration is varied between 10 and 90 vol%. The intrinsic activation energy is found to be 120 kJ mol(-1). The transition temperature between regimes I and II is here defined when the fraction apparent to true activation energy equals 0.75. Higher external mass transfer (e.g., by decreasing the diffusion path through the crucible's freeboard), decreasing the sample amounts, and higher CO2 partial pressures for the Langmuir-Hinshelwood reaction type increase the transition temperature. The results show that the transition temperature between regimes I and II conditions is approx. 1,030 A degrees C for 90 vol% CO2.


Keywords

Char, CO2 gasification, Kinetic regime, Model, Spruce bark

Last updated on 2019-20-11 at 05:15