(25d) Study of Dry Beneficiation of Coal Particles in Air Dense Medium Fluidized Bed using CFD-DEM Method

Authors: 
Zhang, Y. - Presenter, China University of Mining & Technology
Wang, J., State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences
Zhao, Y., China University of Mining and Technology
Duan, C., China University of Mining and Technology
Ge, W., Institute of Process Engineering, Chinese Academy of Sciences
Dry beneficiation of coal particles is an effective method of removing the ash, sulfide minerals and other harmful substances from raw coal. In this study, CFD-DEM method was adopted to study the dry beneficiation of coal particles in dense bubbling fluidized bed, where coarse-grained model is employed to simulate the motion of large amount of Geldart B magnetite powders and DEM is employed to model the motion of coal particles. In the CFD-DEM model, the weight function method and the center-count method are used to calculate the solid fraction and velocity of coal particles and coarse-grained magnetite powders, respectively. It was shown that (1) the simulated separation process of coal particles is in a good agreement with the experimental data under both of the superficial gas velocities of 1.5Umf and 1.75Umf; (2) The light particles with densities of 1400kg/m3 and 1700kg/m3 are easily floated to the bed surface while the dense particles with densities of 2300kg/m3 and 2500kg/m3 settle down slowly to the bed bottom at the superficial gas velocity of 1.5Umf. But for the higher velocity of 1.75Umf, the particles with middle densities of 1700kg/m3, 2000kg/m3 and 2300kg/m3 cannot be separated well due to the entrainment of large bubbles; (3) The force analysis indicates that the dense particles of 2300kg/m3 and2500kg/m3 have a greater resistance force from dense medium particles in separation process. In summary, the CFD-DEM method is an effective method for studying dry beneficiation of coal particles.