Experimental investigation of hardwood air gasification in a pilot scale bubbling fluidized bed reactor and CFD simulation of jet/grid and pressure conditions

Abstract

A pilot scale pressurized (50 psi) fluidized bed gasification was performed to investigate the effects of the jet/grid air ratio (5:95–90:10) and equivalence ratio (ER = 0.23–0.45) on the gasification products such as syngas, tar, contaminant gas, and biochar. There was a noticeable effect of the jet/grid ratios on the syngas concentration. An increase in CO, CH4, and C2 gases was obtained at the condition closer to jet/grid = 50:50, whereas a higher jet/grid ratio favored water–gas shift reaction by increasing CO2 and H2 gases under the pressurized condition. The highest lower heating value (LHV) of 7.7 MJ/Nm3 was obtained at the lowest ER = 0.23. Both the jet/grid ratio and ER were important parameters in determining the H2 concentration. The cold gasification and carbon conversion efficiencies were obtained as high as 66% and 94%, respectively. Also, higher temperature and ER promoted a reduction in contaminant gases as well as tar yield. Tar product yield was also reduced significantly after a wet scrubber, and the tar consisted of chemicals of a carbon number less than 13 (≤C12). The gasification biochar was also analyzed and showed an effective carbon sequestration property with a relatively higher surface area (105 m2/g). Furthermore, computational fluid dynamics simulation was performed to determine the effects of different jet/grid air ratio and pressure conditions on the hydrodynamics in the fluidized bed reactor.