Journal
CASE STUDIES IN THERMAL ENGINEERING
Volume 22, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.csite.2020.100756
Keywords
Pine needle; Combustion; Thermogravimetry; Kinetics; Thermodynamics
Categories
Funding
- National Key Research and Development Program of China [2016YFB1200404]
- National Natural Science Foundation of China [51806106]
- Natural Science Foundation of Jiangsu Province, China [BK20170838]
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The combustion characteristics of Pinus Sylvestris pine needle are studied employing thermogravimetric analysis in air. Kinetic and thermodynamic analyses are performed using two model-free methods and one model-fitting method. Results indicate that two peaks and two shoulders occur in the variations of reaction rate with conversion rate. The maximum and average values of reaction rate decrease with heating rate. The combustion process can be divided into three stages with the thresholds of conversion rate alpha = 0.15 and 0.75. The average values of activation energy/pre-exponential factor for stage 1 (0 = alpha < 0.15), stage 2 (0.15 < alpha < 0.75), stage 3 (0.75 = alpha < 1) and the entire combustion process are 163.18 kJ/mol/9.55 x 10(9) min(-1), 166.46 kJ/mol/ 2.13 x 10(9) min(-1), 132.09 kJ/mol/5.67 x 10(6) min(-1) and 156.89 kJ/mol/3.89 x 10(9) min(-1), respectively. The reaction model characterizing stage 1, 2 and 3 is A(1/3), A(1/4) and F-3, respectively. The obtained kinetic parameters can be used to acceptably predict the conversion rate data. The variations of the change in enthalpy (Delta H), Gibbs free energy (Delta G) and entropy (Delta S) with alpha indicate that more favorable reactions occur and more homogeneous or well-ordered products are generated with the progressing of combustion. Besides, the average values of Delta H, Delta G and Delta S vary little with heating rate.
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