Effects of different operating parameters on the syngas composition in a two-stage gasification process

This research used a two-stage fluidized-bed gasifier to investigate the effects of the temperature, equivalence ratio, and steam/biomass ratio on the syngas composition. When the operating temperature in the first stage increased from 700 °C to 900 °C, the proportion of H2 in the syngas increased significantly. After passing through the second stage (900 °C), the syngas produced from the first stage underwent the thermal reaction again, and the proportion of H2 was further increased. When the ER value increased from 0.2 to 0.3, the proportion of H2 in the syngas increased; whereas, when the ER value increased to 0.4, the amount of H2 produced was reduced. For S/B ratio, an increase to 0.5 enhanced the steam content of the gasifier and accelerated the methane-steam reforming reaction, thus producing more H2 (up to 52 mol%). Furthermore, when the operating temperature of the fluidized bed reactor at the second stage was set at 900 °C, the proportion of H2 in the syngas could still be effectively improved to more than 42 mol% although the operating temperature at the first stage was only 700 °C. The proportion of H2 was enhanced to more than 52 mol% with a combination of appropriate ER and S/B ratio values.