Influence of tube configuration on the gas–solid hydrodynamics of an internally circulating fluidized bed: A discrete element study

• Gas–solid flow dynamics in a baffle-type ICFB with immersed tubes are studied.
• Variation of solid circulation time with the change of tube number is identified.
• Influence of tube number on the solid residence time in the chambers is quantified.
• Influence of tube number on the solid mixing behavior is clarified.
• Erosion pattern around the circumference of each tube is addressed.

Three-dimensional modeling of the gas–solid flow in an internally circulating fluidized bed is conducted by means of the computational fluid dynamics combined with the discrete element method to explore the effect of the tube bundle on the gas–solid hydrodynamics of the system. Gas motion is resolved at the computational grid level, while solid motion is obtained in the Lagrangian view. The influences of tube bundle on the interaction of two chambers, the circulating and resident behaviors of solid phase are evaluated. Moreover, solid mixing behavior and tube erosion are discussed. The results show that the immersed tubes obviously enlarge the gas/solid velocity in the vicinity of the partition plate and lower the interaction intensity of the two chambers. Solid cycle time of the system with or without tubes processes a log-normal distribution. Furthermore, different resident behaviors of the solid phase can be obtained in the two chambers, and inserting the tube bundle in the reactor chamber enlarges the solid residence times of the two chambers. More tubes inserted into the bed enlarge both the cycle time and residence time of the solid phase. On the other hand, the presence of tube bundle enhances the solid mixing intensity. Finally, different erosion distributions appear around the circumferential positions of each tube, and the latent erosion pattern can be identified from the distribution of the time-averaged solid flux.

(a) Snapshot of solid motion at time instant of t = 8 s of the ICFB with 5 tubes locating in the RC and (b) vector plot of the time-averaged solid velocity of the ICFB with 5 tubes locating in the RC.Figure optionsDownload as PowerPoint slide