A mathematical model has been developed to predict performance of a continuous entrained-bed and bubbling fluidized-bed hot gas desulfurization system in IGCC. The model combines the particle residence time with the kinetic rate in each reactor. The model has been applied to the KIER's laboratory scale fluidized bed process. The present model provided a reasonable fit in predicting experimental results that the outlet concentration of H(2)S from the desulfurizer and SO(2) from the regenerator increased nearly proportionally to the inlet concentration of H(2)S to the desulfurizer. The model also could predict well the outlet concentration of O(2) from the regenerator to decrease as the inlet concentration of H(2)S to the desulfurizer increased. The present model predicted with reasonable accuracy mean diameter of bed particles and sulfur content of particles in desulfurizer and regenerator. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.