This paper focuses on the CFD simulation of a CFB pilot-scale carbonator of a 1 MWth DFB installation located at TU Darmstadt (TUD). The carbonator riser height and diameter are 8.661 m and 590 mm, respectively. The state-of-the -art TFM approach is applied while the inter-phase drag coefficient is simulated using a new configuration of the sub-grid EMMS drag model. This configuration incorporates a new approach for the determination of the clusters diameter taking into account the geometrical limitations that the riser diameter poses to the meso-scale structures. The conventional Gidaspow model and the EMMS scheme are tested simultaneously along with the grid density effect. Two mesh densities, one coarse, and one dense are applied, i.e. 31,207 and 285,369 hexahedral elements. The mean ratio of the equivalent cell size to particles diameter (Dcell/Dp) is 465.64 and 222.67, respectively. Except for the grid density effect on the solution results, the wall treatment boundary conditions are investigated, as far as particulates are concerned, through a parametric study on the specularity coefficient values (0.01, 0.1, 0.6 and 0.99) implemented in the partial slip model. Finally, the heterogeneous carbonation reaction is incorporated to the model and a study of the influence of the hydrodynamics on the carbon dioxide capture is investigated. Simulation results are averaged over a time period of 15 s, while the pressure measurements are compared with the corresponding experimental data. Results for pressure converge well with the experimental results for pressure measurements along the riser, when the EMMS model is applied, while it is worth mentioning that this drag model reproduced an almost grid independent solution. For the CO2 concentration at the riser exit, the averaged for 65 s value converges well with the respective measured value.