Numerical investigation of the time-related properties of solid phase in a 3-D spout-fluid bed

• Solid residence time is numerically extracted in a spout-fluid bed.
• Influences of operating parameters on the solid mixing is studied.
• Distribution profile of solid cycle time in the whole system is illustrated.
• Distribution of local residence time in different regions is presented.
• Influence of operating parameters on the local SRTs in three regions is discussed.

Numerical simulation of the two-phase flow in a 3-D spout-fluid bed is carried out to investigate the time-related properties of solid phase based on the In-house code by CFD–DEM coupling approach. The mixing time, distribution properties of the cycle time, global residence time and local residence time of solid phase are explored. Moreover, the influences of spouting gas velocity, background velocity, particle diameter and bed thickness on these properties are discussed. The results illustrate that the mixing time is lowered with the increase of spouting velocity or the decrease of background velocity. Cycle time shows a log-normal distribution behavior and grows with the increase of the particle diameter but decreases with the increase of spouting velocity or background velocity. Moreover, nearly 60% of the total particle time elapses in the annulus and 34% of that in the fountain while only 6% of that is paid in the spout. The solid residence time (SRT) in the spout or annulus diminishes with increasing spouting velocity or background velocity and also the decrease of particle diameter. However, the SRT in the fountain region shows the opposite response behavior. The scale-up of the bed thickness enlarges the cycle time and SRTs in three regions of the bed. Besides, small local SRT appears in the spout while large value exists in the annulus especially the corners of the bed bottom. The geometrical configuration of the bottom leads to the opposite distribution of local SRT near walls in the annulus and fountain. Moreover, the local SRTs in different regions of the system show distinct distribution properties.

(a) 3-D view of the spout–annulus interface with voidage value of 0.7; (b) snapshot of solid motion in the slice of Y = 0.042 m.Figure optionsDownload as PowerPoint slide