Gasification of oil palm residues (empty fruit bunch) in an entrained-flow gasifier

Abstract

Empty fruit bunch (EFB) biomass, one of the most abundant biomass residues in Southeast Asia, was gasified using H2O (steam) or H2O+O2 as a gasification agent in an entrained-flow gasifier at 900°C. During gasification with H2O alone, the EFB gasification rate was >95% (C-equivalent), and hydrogen-rich gas with a composition suitable for liquid fuel synthesis ([H2]/[CO]≈1.8–3.9, depending on the [H2O]/[C] ratio) was obtained. The gasification rate improved (to >99%) when O2 was added to H2O; however, under these conditions, the gas composition was less suitable for liquid fuel synthesis (the amount of [CO2] increased, the amounts of [CO] and [H2] decreased, and the [H2]/[CO] ratio decreased). Nevertheless, the [H2]/[CO] ratio was sufficient (∼2) for liquid fuel synthesis. We also performed thermogravimetric (TG) analysis of EFB using a thermobalance specially designed for analysis of feedstock in the presence of O2, H2O, or both. TG analysis suggested that EFB decomposed easily, especially in the presence of H2O and/or O2. The results obtained from TG analysis and gasification agreed well. In gasification, the tar yield was low (<0.1wt.%), and the tar was composed mainly of six compounds, including naphthalene; these results suggest that the primary tar decomposed and that gasification proceeded quite well. The yield of solid residues was low, and the soft, yellow residues, which partially adhered to the gasifier wall, were composed mainly of ash. These solid residues would require treatment in a large-scale gasifier.