Pyrolysis Kinetics, Thermodynamics, and Volatiles of Representative Pine Wood with Thermogravimetry–Fourier Transform Infrared Analysis
Xiaokang Xu, Ruiyu Chen, Renming Pan, Dongdong Zhang
Abstract
To provide guidance for converting pine wood into fuel or chemical raw material by pyrolysis, the kinetics, thermodynamics, and volatiles of pine wood (Pinus sylvestris var. mongolica) are studied using thermogravimetry and Fourier transform infrared analysis with heating rates from 5 to 40 K/min. The model-free method combined with the model-fitting method is used to estimate the kinetic triplets and thermodynamic parameters. The pine wood pyrolysis in the conversion rate range of 0 ≤ α ≤ 0.9 may be regarded as a single-step reaction. The average values of the activation energy and pre-exponential factor are 181.20 kJ/mol and 6.84 × 1011 s–1, respectively. The reaction model and mechanism for pine wood pyrolysis in the range of 0 ≤ α ≤ 0.9 may be g(α) = [1 – (1 – α)1/3]2 and diffusion, respectively. Based upon the estimated kinetic triplets, the simulated curves of the conversion rate α and reaction rate dα/dT are in good agreement with the experimental curves at multiple heating rates. All values of ΔH and ΔG maintain at a positive constant, whereas all values of ΔS are negative. In addition, the volatiles are mainly generated in the range of 0 ≤ α ≤ 0.9, and the evolution of volatiles is consistent with that of the reaction rate curves. The concentration of the major volatiles in the sequence from highest to lowest is formaldehyde > methanol > methane > CO2 > CO. Moreover, the concentration of formaldehyde is nearly twice that of methanol and 3 times that of methane.