This paper presents a numerical study on the particle dispersion in a horizontally vibrating vessel with round corners under zero gravity. Such a vessel is specifically designed for particle handling in the outer space. The numerical model is validated by good agreement between the simulated and experimental results. The effects of key variables, including overall particle number concentration and vibration amplitude and frequency, are studied by a series of controlled numerical experiments. The particle flow in the vessel is analyzed by the detailed particle scale information obtained from the simulations. The results are used to reveal the mechanisms and clarify some speculations of the particle flow observed in the experiments. In particular, it is found that the conveying velocity generated by the round corner can be correlated to the velocity amplitude, and so is the overall kinetic energy of the particles inside the vessel. The findings are useful for the optimum design of an effective technique for particle transportation under microgravity.