Numerical Study Of The Effect Of Internals On The Gas-Solid Two-Phase Flow In A Fluidized Bed

As an important reactor,gas-solid bubbling fluidized bed is widely applied in the energy,chemical,and pharmaceutical processes.The gas-solid bubbling fluidized bed is characterized by its multi-scale structure,which included the microscale particles,and the mesoscale bubbles.In the gas-solid bubbling fluidized bed,the behavior of bubbles,like the bubbles’ spatial distribution and their physical properties,is essential for the excellent gas and solids mixing and rapid mass and heat transfer.The complexity of the gas-solid flow structure has also been challenging to researchers to further explore the bubble dynamic,the solids mixing properties in the fluidized bed.Numerical modeling of multiphase flows in a fluidization process has snowballed in recent years with its visualization of the microscopic scale of the gas-solid flow.In this study,the multi-phase Eulerian-Eulerian two-fluid method(TFM)coupled with the kinetic theory of granular flow(KTFG)was used to investigate hydrodynamics of particle flows(Geldart Group B)in a lab-scale fluidized bed.The effect of gas distributors and baffles on the distribution of the gas bubbles and the mixing of gas and solids were investigated under various superficial gas velocities.The numerical model is validated by experimental results for twelve operation conditions which include three gas distributor configurations and four superficial gas velocities(0.4/ 0.6/ 0.8/ 1.0 m/s).Simulation with different gases and particles spanned the range from lab to industrial conditions.The results show the possibility of using the gas and particle in lab conditions to study the industrial fluid coking process.As a vital part of the fluidized bed,the gas inlet distributor configuration greatly influences the gas bubble generation,growing,and coalesce,which further greatly impacts the gassolid hydrodynamics in terms of solids mixing and heat transfer.The gas distributor configuration and angle were found to have a significant impact on the gas bubble distribution in this study.And the effect of the inlet gas distributor is much more substantial for distributors with a significant inclined angle.Baffles are used to modify fluidized bed hydrodynamics and to improve the efficiency of industrial processes.This work simulated the impact of various baffles on fluidized bed hydrodynamics.A ring baffle can redirect gas bubbles and induce strong liquid recirculation currents.Baffles can increase the gas holdup throughout the bed.Adding a vertical fluxtube to a baffle can significantly modify its impact on the gas flow patterns.With a fluxtube that does not extend past the baffle lip,the gas is more evenly distributed in the fluidized bed.The fluxtube length has a stronger impact than the fluxtube diameter on the fluidized bed hydrodynamics.In a bubbling fluidized bed,intense and even solids mixing can help minimize the formation of wet agglomerates and further improve the reaction rate and product yield.New methods were developed to characterize the gas and solids mixing patterns from the simulation results.Gas and solids mixing in both horizontal and vertical directions are affected by the gas distributor configuration and the presence of a ring baffle.The ring baffle separates the bed into two regions and reduces the back mixing of gas and solids between the western and eastern regions.Based on the numerical simulation,the numerical results show great agreement with the experimental results.This study comprehensively explored the gas-solid flow,bubble dynamic,solid mixing,and gas mixing in the bubbling fluidized bed,which has certain guiding significance for the industry.