Title:
Reaction Kinetics Study of Willow Char Gasification with CO2 Using TG Analysis
Author(s):
Meng, X., de Jong, W., Fu, N., Verkooijen, A.H.M.
Document(s):
Paper
Abstract:
Gasification kinetics of willow char with CO2 was investigated using thermogravimetric analysis (TGA). Two different types of char samples have been tested. Char one (PYR-Char) was obtained after willow pyrolysis in a TGA at a final temperature of 750 or 850 °C for 20 min. Char two (CFB-Char) was obtained after willow gasification in a 100 kWth circulating fluidized bed (CFB) steam-O2 blown gasifier within the temperature range of 750 to 820 °C with a steam/biomass mass ratio of 1.0 to 1.2 and oxygen to biomass stoichiometric ratio of approximate 0.38. The influences of pyrolysis temperature (750, 850 °C), heating rate (10, 30, 50, 70°C /min), CO2 concentration (10, 20, 30 vol. %) and gasification temperature (900, 1000, 1100 °C) on the reaction rate of char-CO2 reaction were determined. Two representative gas–solid reaction models, the volumetric reaction model (VRM) and shrinking core model (SCM) were applied in order to determine kinetic parameters. It was found that generally char gasification rate increased with increasing gasification temperature, CO2 concentration and heating rate, but decreased with increasing pyrolysis temperature. Generally the calculated activation energy (Ea) values using SCM were slightly lower than those using VRM. The calculated Ea value for PYR-Char using both model were in the range of 90 to 160 kJ/mol, while the calculated Ea value for CFB-char were in the range of 80 to 120 kJ/mol. Scanning electron microscopy (SEM) was employed to observe the willow char structure. The results indicated that CFB-Char was more fragile and PYR-Char obtained under lower heating rate had high condensation or cross-linking of fragments of the side chain. Finally the predicted results using both models showed a fairly good agreement with experimental results in particular with those obtained at lower gasification temperature and lower CO2 concentration.
Keywords:
thermogravimetric analysis, char gasification, volumetric model, shrinking core model
Topic:
Biomass Conversion Technologies for Heating, Electricity and Chemicals
Subtopic:
Gasification for synthesis gas production
Event:
19th European Biomass Conference and Exhibition
Session:
VP2.4.6
Pages:
1551 - 1557
ISBN-13:
978-88-89407-55-4
ISBN-10:
88-89407-55-7
Paper DOI:
10.5071/19thEUBCE2011-VP2.4.6
Price:
FREE
