Performance Evaluation of a Lab-Scale Fluidized Bed Gasifier Using Switchgrass as Feedstock

Abstract

The goal of this study was to evaluate performance of a 2 to 5 kg h-1 laboratory-scale fluidized bed biomass gasifier (FBBG) using switchgrass as a biomass feedstock. The main components of the FBBG system were a biomass feeding unit, a fluidized bed gasifier, an air supply unit with preheater, an air pressure regulator, two cyclone separators, an orifice plate, and a jet-type self-aerated producer gas burner. Silica sand was used as a bed material. Experiments were conducted to evaluate the effect of equivalence ratio (ER) on the reactor temperature profile, energy efficiencies, and producer gas yield and quality such as gas composition and particulate contents. An ER of 0.32 was found to be optimal with a producer gas higher heating value of 6.6 MJ Nm-3 and tar and particulates contents of 4.28 and 0.13 g Nm-3, respectively. The cold and hot gas efficiencies at the optimal condition were 71% and 75%, respectively, and these efficiencies decreased on either side of the optimal value of ER. Both gas yield and carbon conversion efficiency were found to be in positive correlation with ER, with maximum values of 2.5 Nm3 kg-1 biomass (d.b.) and 96%, respectively, at an ER of 0.45.