Hot-gas pyrolysis of fresh palm fruit using a cross-draft biomass gasifier–burner: Product recovery, fuel properties, energy performance, and emissions

Abstract

Conventional biomass pyrolysis commonly relies on electric furnaces or liquefied petroleum gas (LPG) burners as external heat sources, which limits its practicality for decentralized applications in biomass-rich areas. To reduce dependence on these external commercial energy sources, this study investigated the pyrolysis of fresh palm fruit (FPF) using hot exhaust gas from a cross-draft biomass gasifier–burner as the heat source. The effects of pyrolysis temperature on product yields, pyrolysis oil properties, process energy performance, and gaseous emissions were evaluated at 450, 550, and 650 °C. The results showed that temperature strongly affected product distribution. The pyrolysis oil yield increased from 31.8 wt% at 450 °C to a maximum of 36.3 wt% at 550 °C, then decreased to 25.4 wt% at 650 °C, while gas formation increased at higher temperatures because of intensified secondary cracking. At 550 °C, the process achieved the highest oil mass of 11.10 kg, oil energy conversion efficiency of 82.25%, and overall pyrolysis efficiency of 46.84%. GC–MS analysis showed that the oil obtained at 550 °C was dominated by phenols (32.40%), followed by alkanes (28.55%) and alkenes (18.00%), indicating a chemically complex liquid containing both oxygenated and hydrocarbon-type compounds. The separated oil phase had a lower heating value of 39.2 MJ kg⁻¹ but remained acidic, suggesting that further upgrading would be required before practical fuel use. CO and NOx emissions increased with pyrolysis temperature but remained below the Thai regulatory limits. Among the tested temperatures, 550 °C was found to provide the optimum operating condition, as it produced the highest pyrolysis oil yield, oil energy conversion efficiency, and overall pyrolysis efficiency while maintaining CO and NOx emissions below the Thai regulatory limits.