Effect of the type of bed material in two-stage fluidized bed gasification reactors on hydrogen gas synthesis and heavy metal distribution

Abstract

Different bed materials were tested for two-stage fluidized bed gasification, and the hydrogen gas composition and heavy metal distribution in the syngas were investigated. Silica sand, zeolite, calcium oxide, calcined coal, and activated carbon were used. For the results, using activated carbon resulted in the most significant increase in hydrogen after second stage (16.3 mol%) and had highest ratio of hydrogen gas in the syngas (53.1 mol%). For distribution of heavy metals, using activated carbon as bed material in the second stage, the concentration of trapped heavy metals was the highest. Regarding the emission of heavy metals, the use of calcined coal and silica sand resulted in the greatest emission concentration, and activated carbon had the lowest emission concentration. Therefore, to increase the amount of hydrogen gas produced in the gasification process and limit the emission of heavy metals, activated carbon is the best choice of these five bed materials.