Paste Residence Time in a Spouted Bed Dryer. III: Effect of Paste Properties and Quality Interactions

Tacon, Luciana A.; Freitas, Luís Alexandre Pedro de

doi:10.1080/07373930701370225

Cited by 9 publications

(15 citation statements)

References 11 publications

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“…In general, there is a small influence of particle size on the maximum spoutable bed height, which is in agreement with previous reports (Berni and Freitas, 2007;Marreto et al, 2007;Tacon and Freitas, 2007) and there is also an effect on the minimum spouting air flow rate, V ms . The values of V ms increase with dimensionless bed height.…”

Section: Maximum Water Evaporation Capacitysupporting

confidence: 89%

“…This result agrees with the observation of other authors (Barret et al, 1985;Osorio-Revilla et al, 2004) which showed higher volumetric evaporative capacities for SBs when compared to spray-dryers. However, many authors have reported that the maximum evaporation capacities drop dramatically when drying pastes, solutions, and suspensions in SBDIs (Berni and Freitas, 2007;Marreto et al, 2007;Tacon and Freitas, 2007). Nevertheless, the determination of MWEC in SBDI is not an easy task.…”

Section: Maximum Water Evaporation Capacitymentioning

confidence: 95%

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Analysis of pressure fluctuations during water evaporation in spouted bed

et al. 2009

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The aim of this work was to study the behaviour of conventional spouted beds during water evaporation and to analyze the pressure fluctuations at the maximum water evaporative capacity for different bed heights and air flow rates. The results showed that spout pressure drop could not indicate the proximity of maximum evaporative capacity; however this condition is denoted by a minimum in fountain height. The standard deviation and amplitude of the pressure fluctuations also showed a minimum point at the maximum water evaporation capacity. The frequency domain analysis of pressure fluctuations revealed that the dry bed has a dominant frequency varying from 6 to 8.2 Hz and that the peak of dominant frequency tends to disappear with the increase in water feed rate.

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Section: Maximum Water Evaporation Capacitysupporting

confidence: 89%

Section: Maximum Water Evaporation Capacitymentioning

confidence: 95%

Analysis of pressure fluctuations during water evaporation in spouted bed

et al. 2009

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“…1 it can be observed that residence time of chitosan paste in the bed was approximately 15 min in all experiments. The residence time values obtained in this work were in the range with those found by Tacon and Freitas (2007), from 12.2 to 17.7 min, in spouted bed drying of pastes. The outlet air drying temperatures had a similar behavior in both geometries (Fig.…”

Section: Drying Operationmentioning

confidence: 50%

Drying of chitosan in a spouted bed: The influences of temperature and equipment geometry in powder quality

Dotto

Souza

Pinto

2011

LWT - Food Science and Technology

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a b s t r a c tThe influence of temperature and spouted bed geometry in drying chitosan with relation to powder quality (molecular weight, deacetylation degree, particle size, color) and operation characteristics (product recovery and mass accumulated) were investigated. Chitosan paste was obtained from shrimp wastes and dried in a spouted bed (slot-rectangular and conical-cylindrical geometries) with different inlet air temperatures (90, 100 and 110 C). Thermogravimetric curves, infra-red analysis and scanning electron microscopy were carried out in order to verify powder quality. Chitosan paste used in drying experiments showed solid content 4%, molecular weight 140 kDa and deacetylation degree 85%. In all drying experiments deacetylation degree was not modified and final moisture content was in the commercial range (10%). Temperature increase caused an increase in molecular weight, powder darkening and increased particle size. The best powder quality was obtained in slot-rectangular spouted bed at 90 C. In this condition product recovery was 65%, accumulated mass was 20% and the powder presented faint yellow coloration, high thermal stability and porous heterogeneous surface.

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“…The difference between the results of these authors and those obtained in the present work was probably due to the location of the spraying nozzle, since the common distinguishing factor of the two dryers used in the present work (CSB and S-FBDT) was the location of the spraying nozzle. On the other hand, comparing the results of this work with those reported by Berni and Freitas (2007); and Tacon and Freitas (2007), it can be seen that the only difference was the effective presence of a bypass due to the form of feeding the liquid solution. In the present work, the use of a spraying nozzle and the position of this nozzle (above the bed of solids) effectively produced a bypass that can be attributed to the spray drying of fines formed by the spraying nozzle that short-circuit the bed of solids.…”

Section: Resultsmentioning

confidence: 46%

Residence time distribution in spouted bed drying of maltodextrin solutions on a bed of inert particles

et al. 2011

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Residence time distributions (RTD) for aqueous maltodextrin solutions were determined in two kinds of spouted bed dryers: (1) conventional spouted bed (CSB) 0.305 m diameter with a bed of polypropylene beads and (2) spout-fluid bed 0.143 m diameter with draft tube submerged in a bed of FEP ® pellets (S-FBDT). RTD, mean residence time t m , and spread of the distribution 2 , were determined at different drying temperatures, spouting velocities, bed depths, spraying pressures, and feed concentrations. Average values of t m and 2 were 6.5 min and 26.6 min 2 for the CSB and 6.9 min and 36 min 2 for the S-FBDT, respectively, for all operating conditions except spraying pressure. RTD curves were well represented by the response of an ideal stirred tank with a superimposed bypass of 15% on average for the CSB and 7% on average for the S-FBDT dryer for all operating conditions. Increase in spraying pressure produced a reduction of t m and an increase in the bypass fraction of the product in both dryers.

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Paste Residence Time in a Spouted Bed Dryer. III: Effect of Paste Properties and Quality Interactions

Cited by 9 publications

References 11 publications

Analysis of pressure fluctuations during water evaporation in spouted bed

Analysis of pressure fluctuations during water evaporation in spouted bed

Drying of chitosan in a spouted bed: The influences of temperature and equipment geometry in powder quality

Residence time distribution in spouted bed drying of maltodextrin solutions on a bed of inert particles

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