In this paper, the CFD-DEM coupling method was used for the large coal particles simulation. It was found that the axial velocity of particles was symmetrically distributed along the radial direction, and the tangential velocity was distributed symmetrically along the axis of the pipe. The concentration of coal particles in central region is conducive to maintaining large particle integrity and reducing pipe wear. The static pressure drop reflects the instantaneous energy consumption of the conveying system, and the total pressure drop calculated by the integral represents the total energy consumption. The standard deviation of static pressure reflects the degree of particles dispersion in the pipeline, and the high degree of dispersion is more conducive to convey. Based on all the above factors, when conveying large coal particles with 5 mm <= d(p) <= 15 mm, the range of optimum swirl number is 0.3 <= S-o <= 0.4. (C) 2019 Elsevier B.V. All rights reserved.