Numerical Simulation Of Hydrodynamics, Heat Transfer And Combustion Properties In Fluidized Bed Using Discrete Element Method

The wide application of fluidized bed in industry made the hydrodynamic of dense gas-solid two-phase flow become an important research field of multiphase flow. A great deal of experiments and theoretical studies have been carried out all over the world. But due to the complicated effect factors and not yet clarifying the mechanism of two-phase flow, so the traditional experimental method is limited on certain extent. With the rapid development of computer technology, the computer numerical simulation of dense gas-solid two-phase flow has become an important research means.At present, the methods used to simulate dense gas-solid two-phase flow can be divided into two categories: Eulerian-Eulerian approach and Eulerian- Lagrangian discrete particles approach. In this paper, Eulerian-Lagrangian approach is used to establish a serial of models to simulate the gas-solid flow, heat transfer and coal combustion in fluidized bed at particle level. And a CFD-DEM numerical code has been developed.Firstly, the single spouted fluidized bed was simulated and acquired the pressure drop line. The height of solid bed, the generating frequency of bubble and the ascending velocity of bubble at different spouted gas velocity were also obtained. And the quasi-ordering structure in fluidized bed was observed. Besides, the distribution of gas and particle velocities was obtained. The velocity distribution indicated that there is phenomenon of intensive particle back-mixing and internal recycle. A sensitivity analysis was carried out on effects to bubble characteristics due to different particle parameters.Afterwards, the heat transfer and coal combustion properties in fluidized beds was simulated at particle level and obtained the distribution of gas temperature and gas species. The simulation indicated the intensive heterogeneity of the gas-solid flow and coal combustion in fluidized bed. The heating rate of particles and four different particle heat exchange modes were studied. And the sensitivity analysis was carried out on effects to combustion and heat transfer properties due to different particle parameters.Finally, the work of this paper and the further research were summarized.