Theoretical analysis and numerical simulation of the gas-solid hydrodynamics in pressurized bubbling fluidized beds

The heterogeneous structure is considered to improve the theoretical prediction of gas-solid hydrodynamics in pressurized bubbling fluidized beds. The two-fluid simulation shows that the traditional unmodified Gidaspow model overestimates the gas-solid coefficient and bed expansion. As a comparison, the simulations which consider the meso-scale structures predict the reduced gas-solid drag coefficients and the reasonable bed expansions especially at high superficial gas velocities. The decrease in the dimensionless gas-solid drag coefficient with the elevated pressure indicates that the drag modification based on the heterogeneous structure is essential. The parameter sensitivity analysis demonstrates that the effect of the elevated pressure on the gas-solid drag force should be mainly attributed to the changes in minimum fluidization velocity, while the bubble behaviors contribute slightly. Moreover, the gas-solid slip velocity shows a surprisingly uniform distribution, which verifies the dynamic steady state of gas-solid interaction in bubbling fluidized beds.