The scrubbing-cooling chamber is an important part of a coal gasifier to wash and cool the generated high-temperature syngas. It is composed of a vertical pipe and the liquid bath. However, some technical problems still exist in industrial-scale scrubbers, such as unstable operation, lower washing efficiency, all of which are relevant to gas dispersion in scrubbers. It is of great significance to design a scrubbing-cooling chamber with higher washing efficiency. Due to the difficulty of transforming the scrubbers on an industrial-scale, the CFD simulations were used to understand the complex gas-liquid flow in different structures of scrubbing-cooling chambers and to provide theoretical guide for industrial design and process scale-up. In this work, a new scrubber which combined of branch pipes and a draft tube on the basis of the general scrubbers was proposed to promote gas dispersion and a three-dimensional Euler-Euler two-fluid model was used to simulate the flow behavior in three different scrubber geometry, i.e., no-internals, branch pipes attached on the vertical pipe, a combination of branch pipes and a draft tube. Gas holdup, liquid flow field and gas distribution were compared among the three different geometries. Comparison between the simulation and the experiments in literature showed that the model can accurately predict the gas holdup distribution. Furthermore, simulations indicated that the added branch pipes diverted a portion of gas to the central region of the chambers, which may otherwise be entrained along the wall of the central pipe. The branch pipes promoted the radial dispersion and was helpful to maintain stable operation. Further installation of a draft tube enhanced the amount of gas transported by the branch pipes, and increased the global gas holdup under the liquid surface of the scrubber. It was found that the combination of the branch pipes and the draft tube can effectively intensify gas-liquid circulation and interfacial contact, and improve the washing efficiency.