Heat/mass transfer characteristics and nonisothermal drying kinetics at the first stage of biomass pyrolysis

Biomass pyrolysis can be divided into three stages: moisture evaporation, main devolatilization, and continuous slight devolatilization. This present study focuses on the heat and mass transfer characteristics of biomass in the first pyrolysis stage, which takes place in the range of room temperatur...

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Bibliographic Details
Published in:Journal of thermal analysis and calorimetry 2012-08, Vol.109 (2), p.847-854
Main Authors: Chen, Deng-Yu, Zhang, Dong, Zhu, Xi-Feng
Format: Article
Language:English
Subjects:
Analytical Chemistry
Applied sciences
Biomass
Chemistry
Chemistry and Materials Science
Energy
Exact sciences and technology
Inorganic Chemistry
Measurement Science and Instrumentation
Natural energy
Physical Chemistry
Polymer Sciences
Pyrolysis
Toy industry
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Summary:Biomass pyrolysis can be divided into three stages: moisture evaporation, main devolatilization, and continuous slight devolatilization. This present study focuses on the heat and mass transfer characteristics of biomass in the first pyrolysis stage, which takes place in the range of room temperature to 150 °C. Thermalgravimetric experiments of rice husk and cotton stalk were performed by a synchronic thermal analyzer (TG/DSC). Four nonisothermal drying models were obtained from common isothermal drying models in order to describe the drying behavior of agricultural products. The moisture content of biomass decreased rapidly as the temperature increased and an apparent water loss peak was observed in the temperature range of 65–75 °C. DSC could be regarded as the superposition of three parts: heat flow from moisture evaporation, heat flow from the heat capacity of unevaporated moisture, and heat flow from the heat capacity of dry base biomass. The heat requirements for the dehydration of 1 kg rice husk and cotton stalk were 251 and 269 kJ, respectively. Nonisothermal drying models were evaluated based on the coefficient of determination ( R 2 ) and reduced chi-square (χ 2 ). Page model was found to be the best for describing the nonisothermal drying kinetics. The values of activation energy were determined to be 9.2 and 15.1 kJ/mol for rice husk and cotton stalk, respectively.
ISSN:1388-6150
1588-2926
1572-8943
DOI:10.1007/s10973-011-1790-4