Thermal and compositional properties of treated Tectona grandis

A torrefaction parametric study was conducted on Tectona grandis at varying torrefaction temperatures (240–300 °C), residence times (30–60 min), and particle sizes (2–6 mm) using a full factorial design (FFD). Optimum parameters were obtained through numerical optimization using the response optimizer in Minitab 17. These parameters were used to produce fuel with maximum mass yield (MY), higher heating value (HHV), and energy yield (EY). Proximate, ultimate, and HHV analyses were carried out on the raw and torrefied Tectona grandis samples based on ASTM standards, while Fourier transform infrared (FTIR) spectroscopy was used to determine the various functional groups present in the samples. The optimum parameters obtained were temperature (260 ^°C), residence time (60 min), and particle size (< 2 mm), while the maximum MY, HHV, and EY of the fuel are 70.20%, 23.10 MJ/kg, and 88.07%, respectively. The results revealed that torrefaction temperature has the largest effect on the properties of the Tectona grandis compared to other factors based on FFD analyses. There was a reduction in the volatile matter and moisture content of the raw biomass from 79.26 to 54.90% and 7.23 to 2.87%, respectively, while the fixed carbon and HHV increased from 11.73 to 40.43% and 18.73 to 23.10 MJ/kg, respectively, after torrefaction. The FTIR spectra showed a reduction in O–H and C–O bonds and an increase in C–C and C=C bonds in the torrefied samples compared to the raw samples. The thermochemical properties of the torrefied samples are better than those of the raw biomass.