We conducted a numerical study of the mixed charging process and gas-solid flow in the COREX melter gasifier by combining discrete element method (DEM) with computational fluid dynamics (CFD). A full-scale COREX melter gasifier model was established to investigate the charging and blasting processes. The model was validated by comparing with the experimental results under similar conditions. The particles above the raceway region descended faster than those near the centre and the wall. With increasing gas velocity, a larger high-velocity airflow region was formed at the tuyere inlet with increased raceway area. In addition, mixed charging pattern had a significant effect on radial ore-to-coal ratio. The ratio was larger in areas where the relative thickness of DRI was significantly larger than that of coal, and was large above the raceway. The upper packed bed structure had a negligible effect on raceway shape and size. Nevertheless, the gas velocity distribution in the packed bed was affected by the burden distribution, which had less fluctuation in the region where the burden was evenly distributed. The findings facilitate a better understanding of burden distribution and gas-solid flow in the COREX melter gasifier. (C) 2019 Published by Elsevier B.V.