Eulerian simulations of bubbling and jetting regimes in a fluidized bed

The mode of gas-injection is known to influence the local bubbling and jetting behavior in gas-solid fluidized beds.The resultant bubbling behavior influences the mixing and distribution of the gas and solid phases,which in turn can influence heat and mass transfer,and reaction performance in large-scale gas-solid fluidized beds.In the present work,we simulated unary gas-solid flow of particles differing in density,fluidized using uniform and two-jet distributors at different UG.The predictions are validated using the measured local gas-phase area fraction fluctuations,bubble size distribution,and bubble rise velocity.The effect of the models used for calculation of gas-solid drag(βgs),solids frictional pressure(Psf),and specularity coefficient(φ)on the bubbling characteristics under dense and dilute flow con-ditions are analysed.Under dense bed condition(UG=1.1 Umf),an increase in the Psf and φ led to an increase in solids viscosity,which in turn led to a decrease in the bubble rise velocity and size.In the case of the two-jet distributor,an increase in βgs predicted merging of the larger jets and formation of larger bubbles.Further,to predict the different jetting regimes(isolated jets,breakage/merging of jets,and generation of larger bubbles)at different UG correctly,we show that different βgs models are required.Whereas,in the case of gas-solid flows comprised of particles of different density fluidized with the uniform distributor,a single βgs model predicted the bubbling characteristics reasonably well with measurements.