The axial hydrodynamic behavior in a liquid‐solid circulating fluidized bed

Abstract

Based on experimental results from a 7.6 cm I.D. and 3 m high liquidsolid circulating fluidized bed, the liquikolid circulating fluidization regime has been separated into two zones: the initial circulating fluidization zone and the fully developed circulating fluidization zone. The distinct hydrodynamic behavior and the influence of particle properties in the two circulating fluidization zones have been studied. The overall flow structure in LSCFB, although still somewhat non-uniform, is much more uniform than that in a gas-solid CFB. Our experimental results also show that the axial flow characteristics and the regime transition can be strongly affected by the particle density. The stable operation range of the circulating fluidization system and the influences of some associated factors, such as the solids inventory and the particle density, were also investigated for the first time.A partir de resultats experimentaux d'un lit fluidise circulant liquidesolides de 7,6 cm de diarnetre interieur et 3 m de haut, on a separe le regime de fluidisation circulant liquidesolides en deux zones : la zone de fluidisation circulante initiale et la zone de fluidisation circulante pleinement developpee. On a etudie le comportement hydrodynarnique distinct et l'influence des proprietes des particules dans deux zones de fluidisation circulantes. La structure globale de I'ecoulement dans deux zones de fluidisation circulantes. La structure globale de I'ecoulement dans le LSCFB, quoique toujours legerement non uniforme, est beaucoup plus uniforme que dans un CFB gaz-solides. Nos resultats experimentaux montrent egalement que les caracteristiques d'ecoulement axial et la transition de regime peuvent 6tre fortement influencees par la masse volumique des particules. La g a m e de fonctionnement stable du systeme de fluidisation circulant et I'influence de certains facteurs associes, comme I'inventaire des solides et la masse volumique des particules, ont egalement ete etudiees pourla premiere fois. When the liquid velocity is beyond the critical transition velocity, it would be necessary to separate the entrained particles at the riser top and recirculate them back to the base of the riser column. LSCFB has potential applications in the fields of food processing, biochemical processing, petrochemical and metallurgical processing, etc. (Di Felice, 1995; Liang et al., 1997).Hydrodynamics studies are important to properly design an industrial LSCFB system. The flow characteristics in a LSCFB system has been shown to be very different from a conventional liquid-solid fluidized bed and from a gassolid circulating fluidized bed, as reported in recent studies (Liang et al., 1996;1997). However, a more systematic study is still needed for a comprehensive understanding of the phenomena. For example, little work has been done concerning the effects of the physical properties of the particles, such as particle density, on the hydrodynamics of the system. When Liang et al. (1997) studied the solids flow with two relatively low-density particl...

Effect of Liquid Viscosity and Solid Inventory on Hydrodynamics in a Liquid - solid Circulating Fluidized Bed

“…In the developing flow region, located at the lower portion of the riser, solid acceleration along with a decrease in holdup was evident. At higher total velocity, solid holdup plateaus, which indicates that the solid flow enters into the fully developed zone, and was consistent to the results reported in earlier studies (Liang et al, 1997;Zheng et al, 1999;Vidyasagar et al, 2009). …”

“…It is noted that there exists a similar flow structure in the axial distribution of solid holdup at every section of the riser, for the given primary velocity. Vidyasagar et al, (2009), Zheng et al, (1999, Liang et al, (1997) have also reported a similar axial distribution along the riser. An increase in axial solid holdup, with increase in auxiliary velocity can also be observed, suggesting high significance of the non-mechanical valve combination, with respect to the amount of solids held up axially in the riser.…”

Continuous protein recovery with a liquid–solid circulating fluidized‐bed ion exchanger

“…Ž . ported by Liang et al 1997 andZheng et al 1999 . Figure 5 shows the influence of the superficial liquid veloc-Ž .…”

“…This mechanical valve was preferred over the hydraulic valve Ž . described by Zheng et al 1999 due to the low density of the Diaion HPA25 anion-exchange particles, which made the operation of a hydraulic valve difficult.…”

Radial Particle Profiles in a Liquid‐Solid CFB with Varying Viscosity

“…Recent work has demonstrated that the flow structure of LSCFBs is quite different from either conventional liquid fluidized beds (expanded beds) or gas-solids circulating fluidized beds. In the liquidsolid circulating fluidization, particles tend to distribute uniformly in the axial direction of a riser, except for heavy particles [5], while nonuniformity appears in the radial direction with more particles at the wall [6]. Zheng and Zhu [7] characterized the microflow structure of LSCFB and also compared with that of fast fluidization in the gas-solid circulating fluidized systems.…”