Comparative investigation of spontaneous combustion of biomass, hydrochar, coal and their blends using Wits-Ehac and thermogravimetric analysis

Biomass, hydrochar, coal and hydrochar/coal blends have been proposed as alternative energy sources to coal. Given that the new fuels are derived from biomass, which is highly reactive, it is necessary to investigate their potential for spontaneous combustion (SPONCOM). Through the characteristics of coal discard, biomass, hydrochar, and hydrochar mixed at different ratios with discard coal, this study examined the factors that contribute to SPONCOM. The SPONCOM liability of these fuels was examined using the thermogravimetric analysis (TGA) and the Wits-Ehac index. The physicochemical analysis revealed an increase in the energy characteristic of the hydrochar produced from biomass. All samples showed a transmittance of the C=O stretch, which promotes SPONCOM, according to the results of the Fourier Transform Infrared Spectroscopy (FTIR) analysis. The TGA findings revealed that biomass is highly reactive, while discard coal was found to be non-reactive. A significant correlation was seen between the $T{G_{spc}}$TGspc index and the physiochemical properties of the samples. The Wits-Ehac results showed that biomass had the lowest SPONCOM liability index, while the 50% hydrochar/50% discard coal blend had the highest SPONCOM liability index. There was no correlation between the TGA and Wits-Ehac results, as the Wits-Ehac results showed some inconsistencies, particularly for samples derived from biomass. This study establishes the mechanism responsible for SPONCOM of hydrochar blended with coal in relation to their properties using the TGA. In addition, contributed to the understanding of techniques for predicting the SPONCOM of likely fuels for this application.