Particle-Scale Study of the Effect of Operating Conditions on Spout Deflection Behavior in a Flat-Bottomed Spout-Fluidized Bed

Abstract

Spout deflection is a common instability phenomenon in spout-fluidized beds. The hydrodynamics of spout deflection under several key operating variables, including static bed height (H 0), background velocity (U bg), and reactor column width (W), is investigated by means of the computational fluid dynamic-discrete element method (CFD-DEM) coupling approach. The results show that non-alternating spout deflection can be easily observed when the H 0 is larger than 236 mm or the W is less than 0.14 m in this study. For alternating spout deflection, first, there is an upper limit for its amplitude because of the self-locking phenomenon in the bottom corner. Large W promotes the regularity, while the effects of H 0 on regularity is neglectable. Thirdly, the main frequency of the alternating spout deflection reduces with increasing H 0 and increasing U bg and finally stabilizes at 1.7 Hz. This study sheds light on the design, optimization, and operation of spout-fluidized beds.

Experimental Investigation of Spout Deflection in a Rectangular Spouted Bed by the PIV Method

“…A similar trend has also been reported in the spout-fluidized bed in our previous paper . The underlying reason for this stable amplitude can be attributed to the self-locking phenomenon …”

“…Some conclusions are drawn as follows: A new method is proposed to study the spout deflection behavior by the particle velocity vector field profile. The method is demonstrated to be suitable to characterize the alternating spout deflection. In the alternating spout deflection, the self-locking phenomenon, which has been reported in the spout-fluidized bed in our previous simulation work, was found in experiments for the first time. Specifically, when the spout deflects to a certain degree, particles from one side annulus region cannot enter the spout region due to the increasing horizontal components of the drag force.…”

“…In the alternating spout deflection, the self-locking phenomenon, which has been reported in the spout-fluidized bed in our previous simulation work, was found in experiments for the first time. Specifically, when the spout deflects to a certain degree, particles from one side annulus region cannot enter the spout region due to the increasing horizontal components of the drag force.…”

“…16 The underlying reason for this stable amplitude can be attributed to the self-locking phenomenon. 17 Figure 13 shows the frequency spectra of θ t under different U sp values. The peak frequencies in all pictures are distinct, and the signal strength of these peak frequencies is much stronger than others.…”

“…Yue et al studied alternating spout deflection and non-alternating spout deflection in a spout-fluidized bed by the CFD-DEM. He also first quantified the spout deflection extent based on the gas velocity vector in the spout core and then systematically investigated the effect of some operating conditions on the spout deflection . However, such conclusions and point of views derived from numerical simulations need further support from experimental efforts.…”