Experiment And Simulation Study On The Gas-solid Fluidized Bed

Gas-solid flow systems are an essential part of many chemical processes, and contributions to the understanding of the behavior of such flow systems can significantly enhance the design and, in turn, the productivity of such processes. The objective of this research was to validate Euler-Euler simulations of gas-solid fluidized bed by comparing with experiments. To achieve this objective, bubble fluidized bed with single particles and binary mixture respective was simulated with Euler-Euler model based on further analysis of the model. The results of simulation were compared with those of experiment.Firstly, appropriate setting of grid, boundry and initial condition, under-relaxation factors and time step was obtained by tentative simulation. Then, four representative existing models were studied on characteristic and applicability to different flow structure. It is demonstrated that more heterogonous flow structure happens with hybrid models than that with non-hybrid models. Then the analysis on heterogonous flow structure of bubble fluidized bed was carried out by using Euler-Euler model. The results show that restitution coefficient and drag force are main factors affecting on heterogonous flow structure. The main different influence of restitution coefficient and drag force on heterogeneous flow structure lies in particle agglomeration and bed height, respectively.Base on analysis above, the fluidization process of mono-diameter Geldart D particles has been studied experimentally and numerical simulated with Euler-Euler model using numerical solutions of two dimension and three dimension, respectively. It is demonstrated that the two-dimension simulation results of bed expansion ratio reach the same trend to those experimentally with apparently higher value, and results of power spectrum density of pressure fluctuation calculated using FFT method and bed pressure drop meet an agreement between simulation and experiment. The three dimension simulation results of these aspects are close to that experimentally. From analysis on Froude number and energy characteristic, it can be concluded that less exact reflection of two dimension results on heterogeneous flow structure and energy characteristics than those of three dimension result in this difference.Gas-solid bubble fluidized bed of binary mixture was studied on minimum fluidized velocity, pressure fluctuation, power spectrum and dominant frequency. At the same ratio of volume fraction, minimum fluidized velocity increases with the increasing of mean particle diameter. And amplitude of pressure fluctuation and main frequency decrease accordingly. At the same time the simulation on such system was carried out exploringly. The simulation results reach an agreement with that of experiment from Lu's reference by adjusting drag force between particles.