Biomass gasification plays an important role in finding a solution to the energy crisis, and the fluidized bed (FB) is recognized as an important technique for using biomass. However, this process significantly tends toward bed material agglomeration. Accordingly, the aim of this study is to emphasize the effects of operating conditions and different Na concentrations on agglomeration behavior during FB air gasification. Defluidization time decreases as Na concentration increases from 0.8 to 3%. Defluidization time decreases as temperature and the amount of bed materials increase. In addition, no significant change in the trend for this process occurs as the equivalence ratio increases. Adding CaO and Al2O3 can significantly prolong this process, and the inhibition level follows the sequence: Al2O3 > CaO. The same observations are noted during both incineration and air gasification in the FB at various operating conditions. (C) 2011 Elsevier B.V. All rights reserved.