Abstract：A three-dimensional liquid-solid fluidized bed was numerically simulated by discrete element method (DEM) . The lubrication force was taken into consideration. The influence of the binary mixture, wide size distribution and narrow size distribution on the particle size distribution, particle velocity, particle temperature and particle mixed degree were compared.The results show that large particles tend to move toward the lower part of the bed, while small ones toward the upper part of the bed;compared with narrow size distribution, there are obviously different on the axial velocity of binary mixture and wide distribution in different heights, and particle is lower in temperature and more prone to segregation;the greater the size disparity is between diameter of two particles, the more easily they are separated. On the contrary, the closer the diameter of two particles is, the more difficult they are separated, and thus the better the mixed degree is.

Keywords： fluidized-bed; multiphase flow; particle size distribution; discrete element method; computational fluid dynamics