Investigating the characterization, kinetic mechanism, and thermodynamic behaviour of coal-biomass blends in co-pyrolysis process /

Abstract

Co-pyrolysis of the coal-biomass blend has wide-ranging application prospects in relieving energy crises and environmental pollution. In this study, coal-biomass (hemp, sawdust) blends were prepared at various blending ratios (20-80%) for co-pyrolysis investigating. The coal-biomass blends were characterized using ultimate analysis (CHN), gross calorific value (GCV), Fourier transform infrared spectroscopy (FTIR). The co-pyrolysis of blends was performed in thermogravimetric analyzer (TGA). Furthermore, the synergistic effect in each blend was observed by the deviation between the experimental and calculated data of mass loss (ML), residue left (RL), and maximum mass loss rate (DTGmax). The values of deviation in ML and DTGmax indicated the synergistic effect and inhibitory effect during co-pyrolysis. Kinetic parameters were analyzed by employing the Coats-Redfern method with thirteen integral functions. The activation energy (Ea) for individual coal (100C) was 39 kJ/mol through one and half chemical reaction (F3/2), while individual sawdust (100SD) and hemp (100H) showed 60 kJ/mol through deceleratory reaction mechanism for contracting sphere (R3) and 44 kJ/mol through the second order chemical reaction (F2), respectively. Thermodynamic parameters such as change in enthalpy (ΔH), change in Gibbs free energy (ΔG) showed positive values, while the change in entropy (ΔS) was negative for each coal-biomass blend. The C-SD blends are suitable to produce bio-oil as 100SD contained a larger number of volatiles, whereas the C-H blends are suitable to produce bio-char as 100H produced more residue after co-pyrolysis. Hemp bio-char was further characterized by FTIR, TGA, and SEM-EDX analysis to investigate its potential in environmental and energy applications.