Burden distribution plays a crucial role in controlling gas flow distribution and achieving the stability operation of the melter gasifier in COREX. This work presents a coupled DEM-CFD study on burden formation and gas injection of a COREX melter gasifier (MG), mainly focusing on the effects of inclination angle and shape of the DRI-flaps. A one-eighth MG was simulated and compared with the experimental results. The burdens were analysed in terms of particle segregation index and particle distribution index. It was observed that the particles were unevenly distributed in the circumferential directions. This phenomenon was further enhanced with decreasing flap inclination angles as the burden stream became wider and more separated with decreasing inclination angle. To reduce the uneven distribution of particles, flap shapes were changed. It was observed that the thickness of burden piles was proportional to the area of the flaps. The Arc-shape flap, with a medium size of cross-sectional area, was able to control the uniform distribution of DRI particle and formed a uniform pressure distribution in the circumferential direction. The study shows the importance of flaps to maintain the uniform pressure distribution in the circumferential direction of burden beds for stable operation of the melter gasifier. (C) 2018 Elsevier B.V. All rights reserved.