Influence of Longitudinal Vortex Generator Configuration on the Hydrodynamics in a Novel Spouted Bed

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.

Section: Introductionmentioning

confidence: 99%

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

Yue

Shen

2019

“…Wang et al 14 studied the gas−particle flow behavior in a 3D conical spouted bed using the TFM. Wu et al 15 investigated the gas−solid flow in a cylindrical spouted bed with a pair of spherical longitudinal vortex generators by the TFM. Their results showed that the turbulent kinetic energy of the gas phase in the spouted bed was promoted significantly by the longitudinal vortex.…”

Section: Introductionmentioning

confidence: 99%

Two-Fluid Simulation of a Three-Dimensional Spout-Fluid Bed: Flow Structures, Regimes, and Insight into the Mechanism of Particle–Particle Momentum Transfer

Zhao

Liu

Yin

et al. 2021

Spout-fluid beds are widely used in the process industry due to their facilitation of an efficient contact between particles and gas. In this paper, a two-fluid model (TFM) is set up to reproduce the various flow structures encountered during spout-fluid bed operation. The effects of normal restitution model and gas–solid drag model are assessed by comparing simulation results with the experimental and discrete particle modeling (DPM) data of Link et al. [Link et al. Chem. Eng. Sci. 2005, 60, 3425–3442; Link et al. AIChE J. 2008, 54, 1189–1202.]. Simulation results show that application of an effective restitution coefficient in TFM can improve the accuracy of prediction significantly. The drag model of HKL predicts a more reasonable result than models of Huilin-Gidaspow, BVK, and Syamlal and O’Brien. Analysis on relative contributions of kinetic motion, friction, and collision to particle–particle momentum transfer parameters, namely, particle pressure and viscosity, shows that particle–particle momentum transfer in the spout and fountain regions is dominated by kinetic motion and that in the annulus region is dominated by friction. A transition region between spout and annulus regions is proposed. This region can be delineated using a single parameter of dimensionless collisional particle pressure because in this region, particle pressure is dominated by the collisional contribution. With an increasing spout-fluid ratio, the stable spout–annulus–fountain structure gradually shifts to an unstable bubble–slug structure. The effect of collision increases and extends to the entire bed. Meanwhile, the effects of kinetic motion and friction decrease. When slugs are formed, a rebound in the influence of friction is observed, accompanied by a decrease in the influence of collision.

“…When the jet diameter D = 4 mm, the number of jets is 24, and the nondimensional cross-sectional area of the air inlet is 0.67, the fluidization effect between fluids in the bed is optimal. In the case of spouted beds with LVGs, − the law of fluid flow is explored by changing the number of rows, spacing, and diameter of the spherical generators. The simulation showed that when the number of rows of the spherical generators was 3, the spacing was 10 mm, and the diameter was 28 mm, the turbulence effect of the particles was the strongest.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on the Effect of Three Novel Strengthening Components on Water Evaporation in 3D Spouted Beds

et al. 2021

Self Cite

The hydrodynamics of the gas–solid two-phase flow and vaporization of the water phase in an integral multijet spout-fluidized bed (IMJSFB) and spouted beds with spherical longitudinal vortex generators (LVGs) and an integral swirling blade nozzle (ISBN) was numerically simulated. These three novel strengthening components are adopted for the strengthening of the radial mixing of particles, promoting the uniformity of the flow field velocity distribution, and increasing the water vaporization rate. The simulation results show that the three novel strengthening components can promote the uniformity of fluid flow velocity distribution in beds, and the promotion effect is arranged in descending order as follows: LVGs > swirling blades > multijet. In the case of water vaporization, the LVGs, swirling blade, and multijet mainly promote the vaporization of water near the generators, in the spout zone, and the zone near the side nozzles, respectively. Among them, the swirling blade contributes the most to water vaporization, followed by the multijet and then LVGs. In addition, when the gas inlet velocity and temperature are 11.2 m/s and 520 K, respectively, water vaporization is most obviously boosted.