This study modifies a defluidization time prediction model under the influence of agglomeration inhibition provided by the addition of Al into a fluidized bed system. Operational parameters, such as the Al/Na ratio, temperature, gas velocity, and the particle size of bed materials, were considered by the prediction model developed by Lin et al., and thermodynamic consideration of the Al-Na-Si reaction system revealed the agglomeration mechanism. An exponential decay of f(N) was found with the increase of the Al/Na ratio, and the data analysis gave a regression formula of f(N) = 0.0601 +/- 0.4983*exp [-4.4183*(Al/Na ratio)], with an R-2 of 0.9972. The simulation data generally match well with the experimental results, particularly at lower operation temperatures and Geldart B group's particles, with acceptable average errors of -8.4% and -4.9%, respectively. However, relatively poor matches were found in the cases with different gas velocities, a higher operation temperature (900 degrees C), and a larger particle size (Geldart D group) of bed materials. (C) 2012 Elsevier B.V. All rights reserved.