Effects of second-stage bed materials on hydrogen production in the syngas of a two-stage gasification process

This study investigated the effects of various bed materials (silica, biomass-based activated carbon, coalbased activated carbon, and zeolite) used in the second-stage reactor and different gasification conditions on the H-2 fraction in the syngas. The equivalence ratio was fixed at 0.3, and the temperature in the first-stage reactor was held constant at 500 degrees C. Three temperatures were tested in the second-stage reactor, and the steam/biomass ratio was also tested. As shown in the experimental results, the combination of operating temperatures that gives the optimum percentage of H-2 in the syngas is 500 degrees C/900 degrees C. The highest proportion of H-2 formed at S/B = 0.6. As steam passes into the first-stage reactor, the operating temperature and, subsequently, the gasification efficiency can be lowered. The higher operating temperature of the second-stage reactor nevertheless reintroduced steam into the gasification reaction as it entered, raising the H-2 content significantly. In addition, for the different bed materials used in the second stage, B-AC yielded the highest proportion of H-2 in the syngas exiting the gasifier. The H-2 fraction reached 50.96 mol% when S/B = 0.6 and the operation was carried out at 500 degrees C/900 degrees C. Among the four different bed materials, silica yielded the lowest H-2 proportion of 36.66 mol%. (C) 2020 Elsevier Ltd. All rights reserved.