Experimental investigation of synthetic gas composition in a two-stage fluidized bed gasification process: effect of activated carbon as bed material

In this study, a two-stage fluidized bed gasifier was used to investigate the effect of the equivalence ratio (ER) and steam/biomass ratio (S/B) on the synthetic gas distribution while activated carbon (AC) was added as the bed material in secondary gasifier (Stage II). The experimental results showed that when the empty bed (without the bed material) was used for the Stage II reaction, the hydrogen (H₂) content in the synthetic gas emitted from the Stage II reactor was 2-3 mol% higher than that from the first-stage gasifier (Stage I). It was supposed that using the Stage II reactor prolongs the reaction time and thereby increases the H₂ production. Besides, when the AC was added in the Stage II gasifier, the H₂ concentration, the total gas yield, and gas heating value reached their maximum (30 mol%) when ER and S/B were 0.3 and 1.5, respectively.