Flue gas desulfurization (FGD) in a CFB at moderate temperatures with the T-T sorbent, a hydrated calcium-based sorbent was numerically simulated using the Eulerian approach with two drag models for heterogeneous gas-solid flow, one is an EMMS-based theoretical model (QL-EMMS), the other is an experimental model (O-S). The QL-EMMS model was analyzed in terms of the cluster parameters, the drag reduction and CFB modeling by comparing with the experimental data and results of the O-S model. Results using a heterogeneity index show that the QL-EMMS model is more accurate than other theoretical drag models, but there are still some differences from experimental data due to an inaccurate description of the solid volume fractions in clusters. The factors influencing the moderate temperature desulfurization were then investigated based on the accurate O-S drag model. Predictions of the desulfurization efficiency and reaction rate indicate that higher solid volume fractions and more homogeneous solid distributions lead to higher desulfurization efficiencies. The reaction time also has an important effect on the desulfurization. (C) 2011 Elsevier Ltd. All rights reserved.