L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate ...L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate as well as the hydrodynamics performance of the CFB with L-valve is of great importance for its better control and design.This paper proposes a Eulerian-Eulerian approach based numerical model integrating the computational fluid dynamics(CFD)with turbulent model,the kinetic theory of granular flow(KTGF)and the drag model,thus the solids circulation rate and the local phase velocity as well as solids volume fraction can be predicted simultaneously.With this model,the hydrodynamics perfor-mance of the full loop GSCFB with a L-valve is analyzed in detail.It is found that the drag model affects the simulation significantly and the(energy minimization multiscale)EMMS method shows good per-formance in the full-loop simulation of GSCFB.展开更多
Stable and controllable solid flow is essential in circulating fluidized bed (CFB) systems. The L-valve is a typical non-mechanical valve that can provide flexible solid feeding. The investigation of the solid circula...Stable and controllable solid flow is essential in circulating fluidized bed (CFB) systems. The L-valve is a typical non-mechanical valve that can provide flexible solid feeding. The investigation of the solid circulation rate and the hydrodynamic characteristics of the L-valve is crucial to its design and operation. The gas-solid flow in the L-valve of a full-loop CFB is studied with the coarse-grained discrete particle method (EMMS-DPM). Good agreements on the solid circulation rate and the pressure drop through the L-valve are achieved between the simulated and experimental data. The solid circulation rate increases linearly with the aeration velocity until the stable particle circulation of the CFB is destroyed. The flow patterns in the horizontal section of L-valve are gas-solid slug flow above the stationary solid layer and the moving solid layer, respectively. The effects of L-valve geometric parameters on the solid flow characteristics are also investigated. The results indicate that reducing the diameter and length of the horizontal section of L-valve can improve the solid transport efficiency, especially at low aeration velocity. Besides, the solid conveying capacity and flow stability are improved when the sharp bend of L-valve is modified to be a gradual bend.展开更多
基金support by the National Key Research and Development Program of China(grant No.2018YFE0111100)the National Nature Science Foundation of China(grant No.22078230)the Open Foundation of State Key Laboratory of Chemical Engineering(grant No.SKL-ChE-21B07).
文摘L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate as well as the hydrodynamics performance of the CFB with L-valve is of great importance for its better control and design.This paper proposes a Eulerian-Eulerian approach based numerical model integrating the computational fluid dynamics(CFD)with turbulent model,the kinetic theory of granular flow(KTGF)and the drag model,thus the solids circulation rate and the local phase velocity as well as solids volume fraction can be predicted simultaneously.With this model,the hydrodynamics perfor-mance of the full loop GSCFB with a L-valve is analyzed in detail.It is found that the drag model affects the simulation significantly and the(energy minimization multiscale)EMMS method shows good per-formance in the full-loop simulation of GSCFB.
基金the National Natural Science Foundation of China(grant No.22278404),and the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(grant No.21921005)the National Key Research and Development Program of China(grant No.2023YFC2908002)the State Key Laboratory of Multiphase Complex Systems(grant No.MESO-23-A03).
文摘Stable and controllable solid flow is essential in circulating fluidized bed (CFB) systems. The L-valve is a typical non-mechanical valve that can provide flexible solid feeding. The investigation of the solid circulation rate and the hydrodynamic characteristics of the L-valve is crucial to its design and operation. The gas-solid flow in the L-valve of a full-loop CFB is studied with the coarse-grained discrete particle method (EMMS-DPM). Good agreements on the solid circulation rate and the pressure drop through the L-valve are achieved between the simulated and experimental data. The solid circulation rate increases linearly with the aeration velocity until the stable particle circulation of the CFB is destroyed. The flow patterns in the horizontal section of L-valve are gas-solid slug flow above the stationary solid layer and the moving solid layer, respectively. The effects of L-valve geometric parameters on the solid flow characteristics are also investigated. The results indicate that reducing the diameter and length of the horizontal section of L-valve can improve the solid transport efficiency, especially at low aeration velocity. Besides, the solid conveying capacity and flow stability are improved when the sharp bend of L-valve is modified to be a gradual bend.
