Gasification of Miscanthus x giganteus in an Air-Blown Bubbling Fluidized Bed: A Preliminary Study of Performance and Agglomeration

Abstract

Gasification of Miscanthus x giganteus (MxG) was conducted in an air-blown bubbling fluidized bed (BFB) gasifier using magnesite as bed material and a moderate rate of biomass throughput (246.82–155.77 kg/m2h). The effect of equivalence ratio (ER) (0.234–0.372) and bed temperature (645–726 °C) on the performance of gasification was investigated. The results reveal that MxG is a promising candidate for energy production via BFB gasification; of the conditions tested, the optimal ER and temperature are approximately 0.262 and 645 °C, where no sign of agglomeration was found. The product gas from this condition has a higher heating value of 6.27 MJ/m3, a gas yield of 1.65 N m3/kgbiomass (39.5% of CO and 18.25% of H2 on N2 free basis), a carbon conversion efficiency of 94.81% and a hot gasification efficiency of 78.76%. Agglomeration was observed at some higher temperature conditions and believed to be initiated by the formation of fuel-ash derived low melting temperature K-rich (potassium) silicates (amorphous material that cannot be detected by XRD). It is suggested that relatively low temperature (650 °C) needs to be used for the gasification of MxG to avoid potential agglomeration.