The influence of inert additives and recycling raw gas on biomass gasification in a fluidized bed gasifier

Several important indexes of biomass gasification in a fluidized bed reactor, such as, the higher heating value (HHV), carbon conversion, effective carbon conversion, and energy conversion ratio, were compared under gasification with and without sand. Although these indexes of gasification with sand were 3% to 15% higher than those of gasification without sand, abrasion on the inner surface of the fluidized bed and lower effective reactive cubage were two severe problems. The temperature distribution in the fluidized bed, which was a key factor influencing the gasification, could be improved by raw gas recycling. The temperature was distributed between 150 degrees C and 700 degrees C before and between 450 degrees C and 800 degrees C along the fluidized bed following raw gas recycling. Fifty percent recycled raw gas was effective for improving the temperature distribution in the fluidized bed.