Physicochemical characterization of Thar coal and torrefied corn cob

Abstract

In this study, the corn cob was torrefied at five different temperatures (200, 225, 250, 275 and 300°C) for four different residence times (15, 30, 45 and 60 min). The physical and chemical properties such as proximate and ultimate analysis, true density, grindability and hydrophobicity of Thar coal along with raw and torrefied corn cob were investigated. To examine the changes in the functional groups of torrefied corn cob, more information was taken from spectrometric studies, by using Fourier transform infrared spectroscopy (FTIR). It was found that there is no significant improvement in the physical and chemical characteristics of torrefied corn cob at low torrefaction temperatures of 200 and 225°C, although as the torrefaction temperature and residence time increased, a significant improvement was found in the physical and chemical characteristics of the torrefied corn cob. At the maximum torrefaction temperature (300°C) and longer residence time (60 min), the physical and chemical characteristics of the torrefied biomass were found to be equivalent to Thar coal. The FTIR studies showed that due to torrefaction, the R-OH groups decrease and C=O groups were increased within the fuel. Due to this change, the tendency of corn cob to absorb water decreases and the biomass becomes more hydrophobic in nature. Thus, torrefaction is an effective way to improve the characteristics of corn cob to such an extent that it could be comparable to Thar coal, which is a lignite coal. Previously, different researchers proposed that energy intensification and mass loss of biomass are proportional to the heating temperatures of 200–300°C. All were tinged with uncertainty, as the temperature range is too wide and does not specify a precise effect of different torrefaction temperature towards particular biomass. While the present study gives a point by point comprehensive information, utilizing single biomass (Corn cob), underneath the maximum feasible temperature levels from 200 °C to 300 °C (for example 200, 225, 250, 275 and 300 °C) and residence time (15, 30, 45, and 60 minutes). This comprehensive data may facilitate better optimization of the torrefaction conditions.