Influence of process parameters on thermal characteristics of char from co-pyrolysis of eucalyptus biomass and polystyrene: Its prospects as a solid fuel

The prospects of chars derived from the co-pyrolysis of waste polystyrene (WPS) and eucalyptus biomass at variable temperatures (300–550 °C), residence times (90–150 min) and proportions of WPS (w/w) (33% and 25%) for their potential use as a solid fuel were assessed. The production of char suggested an improved fuel quality compared to the raw feedstock because of reduced volatile and oxygen contents, along with an increase in the carbon and fixed carbon contents. While the properties of the char such as energy density (1.12–1.30), high heat value (28.03–32.5 MJ/kg) had their maximum values observed with 33% WPS content at 300 °C, fixed carbon (4.5–34.19%), fuel ratio (0.05–0.64) were maximum with 25% WPS content at 550 °C. Moreover, the energy yield of the char was higher than the mass yield. The chars produced at 300, 350 °C were observed to have O/C and H/C ratios similar to that of sub-bituminous and bituminous coal. Principal component analysis presented the variable effects of WPS on the properties of the char through physical inhibition and synergistic interactions below and above the complete volatilization temperature of WPS.