Optimization of hhv and energy yield from torrefaction of Albizia zygia wood- calcium hydrogen phosphate catalyst blends using optimal combined design

Abstract

The over-reliance on fossil fuels as a primary source of energy is partly responsible for the increase in carbon dioxide (CO2), depletion of the ozone layer, and general environmental pollution. In this study, torrefaction of Albizia zygia wood-calcium hydrogen phosphate (CaHPO4) catalyst blends was carried out in a tubular furnace to examine the impacts of temperature, time, and particle size on higher heating value (HHV) and energy yield (EY). Albizia zygia wood was obtained at an industrial sawmill junkyard nearby Kwara State University, dried, crushed, and sieved into 1 - 3 mm particle size. Optimal Combined Design (OCD) was employed for the design, modelling, and optimization of HHV and EY under the ranges of selected temperature (200 - 300?C), residence time (15 - 30 min), and particle size (1 - 3 mm) in an inert environment tubular furnace. The results of the analysis indicated that the temperature of 245?C, time of 22 min, and size of the particle 3 mm yielded a maximum HHV of 19.59 MJ/Kg and EY of 76.37% respectively. Also, the addition of catalyst (CaHPO4) at 10% reduced the ash content but enhanced the fixed carbon content of the biochar. The mathematical models for the HHV and EY for the torrefaction using the OCD imply an excellent fit with R2 of 0.92 and 0.96, respectively. The prediction accuracy indicates that OCD can be deployed for the accurate prediction of HHV and EY in torrified biomass.