Global degradation kinetics of pine needles in air

Pine needles are available in large quantities in the hilly region of Himalayas in India. Pine needles have good energy potential for exploitation through pyrolysis and gasification. This paper deals with the thermal degradation characteristics of pine needles and its kinetics. Thermal degradation analysis has been done by using a thermogravimetric analyzer from room temperature to 900 °C in air atmosphere at different heating rates, viz. 5, 10, 15, 25 and 30 K min−1. The TGA, DTG and DTA curves exhibited four distinct degradation zones. However, at the low heating rate of 5 K min−1, only three degradation zones were found. The second, third and fourth zones had higher values of activation energy than the first zone. The kinetic parameters were determined by using several methods proposed in the literature assuming single step, irreversible reaction for a particular zone. Agrawal and Sivasubramanian [AIChE J. 33 (1987) 6] method was found to be most consistent. For the total degradation zone the orders of reaction were found in the range of 0.00–2.50 by using Agrawal and Sivasubramanian [AIChE J. 33 (1987) 6] approximation, the activation energy in the range of 34.60–85.34 kJ mol−1 and the preexponential factor in the range of 3.29×104 to 5.98×106 mg1−n min−1. The relative simplicity of the model gives it the potential for applications in the design of large scale biomass-pyrolysis facility in remote areas.