Hydrogen generation from gasification of woody biomass upon acid mine drainage sludge as a novel catalyst under an air medium

Abstract

In this study, the feasibility of employing acid mine drainage sludge (AMDS), mainly consisting of iron oxide (Fe2O3), as a novel catalyst for the air gasification of woody sawdust to produce H2-rich gas was evaluated for the first time. The effects of temperature, equivalence ratio (ER), and contact mode of the feedstock and catalyst on gas yield and H2 selectivity were investigated. Using the AMDS catalyst, a comparably higher gas yield (56.79 wt%) and higher content of H2 (18.31 vol%) and CO2 (36.45 vol%) were obtained compared to those obtained in the non-catalytic case owing to stimulated water–gas shift and steam–methane reforming reactions caused by the redox cycle of Fe2O3 within the gasification process. Gas yield and H2 concentration were enhanced by increasing the temperature from 750 to 850 ℃ (up to 65.11 wt% and 21.73 vol%, respectively) due to promoted endothermic reactions. Although increasing the ER from 0.1 to 0.3 dramatically increased the gas yield, it was not conducive to the promotion of H2 production, primarily because of the stimulated hydrogen oxidation reaction. The ex situ contact mode, where feedstock and catalyst were placed in the reactor and catalyst bed, respectively, resulted in a higher gas yield and H2 selectivity compared to those achieved by the in situ case, in which a mixture of feedstock and catalysts was located in the same reactor. Overall, the gasification of woody sawdust over an AMDS catalyst in an air medium has the potential to mitigate the challenges of AMDS treatment along with the production of valuable H2-rich gas.