Fluidised bed drying of granular food materials

Thomas, P.; Varma, Y. B. G.

doi:10.1016/0032-5910(92)80012-l

Cited by 37 publications

(15 citation statements)

References 5 publications

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“…They also studied the effect of the superficial gas velocity as well as the operating temperature over the process, and concluded that the higher values of these two parameters, superficial gas velocity and operating temperature, produce a higher rate of drying as a result of lower external resistance to mass transfer. These tendencies fully confirm the conclusions reached by Thomas and Varma [7] as well as Uckan and Ulku [8], in their respective studies performed under atmospheric conditions.…”

Section: Introductionsupporting

confidence: 92%

Influence of Effective Particle Porosity on Vacuum Fluidized Bed Drying

Kozanoglu

Nava

Chanes

2006

Chem. Eng. Technol.

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A series of vacuum fluidized bed drying experiments was carried out employing particles with distinct effective porosities. The experiments showed that decreasing the operating pressure as well as increasing the operating temperature produces higher drying rates in both drying periods. In all cases, the enhancement of the drying rates was found to be more significant in the case of particles with higher effective porosities. It is concluded that lower operating pressures as well as higher operating temperatures help to reduce the formation of air pockets in the pores and postpone the onset of the pendular state, enhancing the capillary action and the drying rates.

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Section: Introductionsupporting

confidence: 92%

Influence of Effective Particle Porosity on Vacuum Fluidized Bed Drying

Kozanoglu

Nava

Chanes

2006

Chem. Eng. Technol.

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“…These tendencies fully confi rm the conclusions reached by Thomas and Varma (1992) as well as Uckan and Ulku (1986).…”

Section: Constant Operating Pressure Experimentssupporting

confidence: 84%

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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“…[13,14] A comparison of the drying rate curves for two sizes of pepper seed particles is shown in Fig. 6.…”

Section: Resultsmentioning

confidence: 99%

“…[11][12][13][14][15][16][17] However, the information on vacuum-fluidized bed drying available in the technical literature is very limited. The first studies to employ a vacuum-fluidized bed dryer were carried out in the pharmaceutical industry.…”

Section: Introductionmentioning

confidence: 99%

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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Fluidised bed drying of granular food materials

Cited by 37 publications

References 5 publications

Influence of Effective Particle Porosity on Vacuum Fluidized Bed Drying

Influence of Effective Particle Porosity on Vacuum Fluidized Bed Drying

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

Influence of Particle Size on Vacuum–Fluidized Bed Drying

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