Thermal Conversion of Pine Wood and Kinetic Analysis under Oxidative and Non-Oxidative Environments at Low Heating Rate

Abstract

Atmosphere is one of the most significant factors in the thermal decomposition of biomass. In domestic or industrial biomass boilers, ambient oxygen concentration varies through time, which means that the reaction will change from pyrolysis to combustion. In this way, to analyze and compare each thermochemical conversion process, a simple analytical method, the non-isothermal thermogravimetric analysis, is carried out under oxidative (air) and non-oxidative (argon) environments at 10 °C/min and as a function of different flow rates (2 to 150 mL/min). Additionally, this work was complemented by a kinetic analysis considering a first-order reaction to each conversion stage and using the Coats–Redfern method. The effect of the atmosphere on the thermal decomposition behavior was evident. It was observed that the thermal decomposition of pine wood particles varied from three to two stages when the oxidative or inert atmosphere was applied. The presence of oxygen changes the mass loss curve mainly at high temperature, around 350 °C, where char reacts with oxygen. The maximum mass loss rate from experiments with the oxidative atmosphere is 15% higher than in an inert atmosphere, the average char combustion rate is approximately 5 times higher and the heat released reaches levels 3.44 times higher than in an inert atmosphere. Ignition and combustion indexes were also defined, and results revealed that particles are ignited faster under oxidative atmosphere and that, on average, the combustion index is 1.7 times higher, which reinforces the more vigorous way that the samples are burned and how char is burned out faster in the experiments with air. Regarding the kinetics analysis, higher activation energies, and consequently, lower reactivity was obtained under the oxidative atmosphere for the second stage (~125 kJ/mol) and under the inert atmosphere for the third thermal conversion stage (~190 kJ/mol).

Medical Peat Waste Upcycling to Carbonized Solid Fuel in the Torrefaction Process

“…The result showed that wood decomposes in two stages. The first stage occurred at 250-390 • C, while the second one was at 390-612 • C. The Ea for these stages were 190 and 117 kJ × mol −1 , respectively [64]. Nevertheless, despite the differences in the observed values, and approaches, the results suggest relatively suitable predictions of conversion in these works.…”

“…Similarly, it is with wood. For example, Fraga et al [64] analyzed the decomposition of wood using the CR method considering only a first-order reaction model (n = 1). The result showed that wood decomposes in two stages.…”

Investigation into the combustion kinetics and spontaneous ignition of sweet sorghum as energy resource

“…In support of the reactivity data, the ignition and combustion indices were calculated for all samples to provide a more accurate measure of the conversion over time and temperature. According to Fraga et al ( 2020b ), the ignition and combustion indices are defined in Eq. 1 and Eq.…”

A Review of Biomass Thermal Analysis, Kinetics and Product Distribution for Combustion Modeling: From the Micro to Macro Perspective

“…According to this model, the kinetic parameters can be determined by the equation presented in Table 4 and neglecting the term 2RT/E, which can be considered much lower than one. The value for A is then determined from the interception of the plot indicated in Table 4 [153], with the possibility to make this analysis at different stages of the conversion process. Otherwise, to complete the determination of the kinetic parameters A and f (α), usually the Kissinger or compensation factor methods and master plots methods have been used to obtain both parameters, respectively [82].…”