Hydrodynamics of large particle fluidization in reduced pressure operations: an experimental study

Kozanoglu, Bulent; Chanes, J. Welti; Cuautle, D Garcı́a; Jean, J.P Santos

doi:10.1016/s0032-5910(01)00524-1

Cited by 29 publications

(15 citation statements)

References 13 publications

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“…The same tendency was also presented by Llop et al [6] and was attributed to the increase of the mean free path of molecules as a result of the lower gas density. In addition, Kozanoglu et al [7] found that the bed voidage at minimum fluidization conditions was not significantly influenced by the operating pressure, as also reported earlier by Chitester and Kornosky. [8] Mawatari et al [9] confirmed that the minimum bubbling and minimum fluidization velocities increased with decreased operating pressure.…”

Section: Introductionsupporting

confidence: 69%

“…In a later study, Llop et al [6] presented two equations to calculate the minimum fluidization velocity over a very wide range of operating conditions, from vacuum to high pressure. Kozanoglu et al [7] experimentally measured minimum fluidization velocity in a vacuum-fluidized bed of large particles. They observed that a decrease in operating pressure increased the minimum fluidization velocity.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Particle Size on Vacuum–Fluidized Bed Drying

et al. 2011

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The effect of particle size on the vacuum-fluidized bed drying process was experimentally studied using pepper seed particles with two distinct diameters. In the constant drying rate period, the small particles demonstrated stronger drying rates resulting from higher mass transfer coefficient values and larger contact area for per unit particle humidity.The experimental results also showed that the falling drying rate period was controlled in the beginning by the particle diameter and later by the effective porosity of the particle. Consequently, in the beginning of the falling drying rate period the small particles presented higher drying rates, whereas toward the end of the period, the large particles, with higher effective porosity, produced stronger drying rates than the small ones.The effects of the vacuum pressure and the superficial gas velocity throughout the process were only observed in the constant drying rate period, whereas the higher operating temperatures enriched the drying rates in both periods.

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Section: Introductionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Influence of Particle Size on Vacuum–Fluidized Bed Drying

et al. 2011

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“…The minimum fl uidization velocity for multi-sized particles fl uidized at vacuum conditions was defi ned by Fletcher et al (1993). Kozanoglu et al (2002a) measured minimum fl uidization velocities of large particles in a reduced pressure operation.…”

Section: Randd Notementioning

confidence: 99%

Stepwise Change of Operating Pressure in Vacuum Fluidized Bed Drying: An Experimental Study

et al. 2008

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F luidization is one of the most attractive processes in the chemical industry. Drying process in a fl uidized bed has various advantages, such as large contact area between particles and fl uid, high rates of heat and mass transfer as well as a very good level of solids mixing that facilitates temperature control.However, application of fl uidized bed drying has been abandoned in some fi elds, such as fi ne chemicals and the pharmaceutical industry, because of problems of thermal degradation and safety. The drying process, at relatively high temperatures or long residence times, may cause the partial degradation of thermolabile products. In addition, if the process is involved with evaporation of an organic solvent, as it is often the case in the pharmaceutical industry, a mixture within the fl ammability limits with a high risk of explosion can be formed. A reduced pressure operation in a fl uidized bed offers the possibility of eliminating these problems. Lower operating temperatures achieved under vacuum conditions reduce the probability of thermal degradation. Simultaneously, the lower pressure operation may provide a safer process out of fl ammability limits. Vacuum-fl uidized bed drying experiments were carried out with porous as well as compact particles, employing distinct operating pressures in two periods of drying, such that the combination of the effects of decrease in the transport capacity of the exterior medium and the enhancement of the internal diffusivity results in favour of the drying process. In a variety of operating conditions, it was observed that in the case of porous particles, increasing the operating pressure during the decreasing drying rate period, after applying a vacuum pressure in the constant drying rate period results in a lower fi nal particle humidity.Des expériences de séchage en lit fl uidisé sous vide ont été menées avec des particules poreuses et des particules compactes, avec des pressions opératoires distinctes pour deux périodes de séchage, de sorte que la combinaison des effets de la baisse de capacité de transport du milieu extérieur et l'amélioration de la diffusivité interne soient favorables au procédé de séchage. Dans diverses conditions opératoires, on a observé que dans le cas de particules poreuses, le fait d'accroître la pression opératoire lorsqu'on diminue la période de décroissance du taux de séchage, après avoir appliqué une pression à vide durant la période de taux de séchage constant entraîne une plus faible humidité fi nale des particules.

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“…Recent experiments and simulations have shown that the addition of inert particles such as sand, glass beads, and alumina can effectively facilitate the fluidization of biomass (Kozanoglu et al 2002;Abdullah et al 2003;Suarez 2003;Zhang et al 2009;Paudel and Feng 2013;Sharma et al 2013;Fotovat et al 2015). Sand as a medium material can also enhance the heat transfer in the process of biomass thermochemical conversion (Rao and Bheemarasetti 2001).…”

Section: Introductionmentioning

confidence: 99%

Fluidization Behavior of Biomass Particles and its Improvement in a Cold Visualized Fluidized Bed

Wu¹,

Li²,

Song³

et al. 2017

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The fluidization behavior in a fluidized bed was visualized at room temperature under different conditions for two typical lignocellulosic biomass materials (rice husk and walnut shell) as representative samples of herbage and xylophyta, respectively. The effects of initial bed height, moisture content, and addition of sand particles on the quality of fluidization were analyzed, and the optimal operating parameters were determined. The initial bed height had a negligible effect on the minimum fluidization velocity but an obvious influence on bed stability. In addition, with an increase in moisture content, the minimum fluidization velocity showed the growth of an S-shaped curve and a constant decrease in the fluidization index in the fluidized region. Fluidization when performed on binary mixtures indicated that the proportion of sand-3 (60 to 80 mesh) in biomass and sand-3 in mixtures is a main factor contributing to the fluidizing quality of a bed. With larger proportions of sand-3, the fluidizing quality of the bed improved. Meanwhile, the differences in fluidization behavior between rice husk and walnut shell have been determined.

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Hydrodynamics of large particle fluidization in reduced pressure operations: an experimental study

Cited by 29 publications

References 13 publications

Influence of Particle Size on Vacuum–Fluidized Bed Drying

Influence of Particle Size on Vacuum–Fluidized Bed Drying

Stepwise Change of Operating Pressure in Vacuum Fluidized Bed Drying: An Experimental Study

Fluidization Behavior of Biomass Particles and its Improvement in a Cold Visualized Fluidized Bed

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