Abstract
This study provides an extensive investigation on the kinetics, combustion characteristics, and thermodynamic parameters of the thermal degradation of guinea grass (Megathyrsus maximus) in N2-pyrolytic and oxidative atmospheres. A model-fitting technique and three different iso-conversional techniques were used to investigate the kinetics of the thermal process, after which an analysis of the combustion characteristics and thermodynamic parameters was undertaken. Prior to this, experiments on the physico-chemical characterization, thermogravimetric, and spectroscopic analyses were carried out to provide insight into the compositional structure of the guinea grass. The volatile matter, fixed carbon, and total lignin contents by mass were 73.0%, 16.1%, and 21.5%, respectively, while the higher heating value was 15.46 MJ/kg. The cellulose crystallinity index, determined by XRD, was 0.43. The conversion of the GG in air proceeded at a relatively much higher rate as the maximum mass-loss rate peak in a 20 K/min read was −23.1 and −12.3%/min for the oxidative and the pyrolytic, respectively. The kinetics investigation revealed three distinctive stages of decomposition with their corresponding values of activation energy. The average values of activation energy (FWO) at the latter stages of decomposition in the pyrolytic processes (165 kJ/mol) were higher than those in the oxidative processes (125 kJ/mol)—an indication of the distinctive phenomenon at this stage of the reaction. The Coats–Redfern kinetic model revealed that chemical reactions and diffusional models played a predominant role in the thermal decomposition process of the GG. This study showed that the thermodynamic parameters varied with the conversion ratio, and the combustion performance increased with the heating rates. The use of GG as an energy feedstock is recommended based on the findings from this work.
Highlights
This article is an open access articleThe excessive utilization of fossil fuel sources for diverse energy purposes engenders a grave global concern
The Coats–Redfern, Flynn–Wall–Ozawa, and Starink techniques were utilized to evaluate the kinetic parameters, and these were subsequently used in the combustion characteristics and thermodynamics analyses
The model-fitting technique suggested that the chemical reaction and diffusional models play critical roles in the thermal decomposition processes of guinea grass (GG), both in the N2 and the air atmospheres
Summary
The excessive utilization of fossil fuel sources for diverse energy purposes engenders a grave global concern. The combustion of these fuel sources results in the emission of greenhouse gases (GHGs), which have been implicated in global warming and climate change phenomena [1,2]. Diverse biomass materials have been investigated through thermochemical means for probable bioenergy applications and biofuel production. These include rice husk, corn cobs [3], sugarcane straw [4], peanut shells [1], sorghum bicolor glume [5], coffee residues [6], and different woody samples [7,8,9]
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