Paste Residence Time in a Spouted Bed Dryer. I: The Stimulus-Response Methodology

Marreto, Ricardo Neves; Peixoto, Maria Paula Garofo; Tacon, Luciana A.; Freitas, Luís Alexandre Pedro de

doi:10.1080/07373930701370191

Cited by 5 publications

(6 citation statements)

References 8 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: 96%

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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: 96%

Analysis of pressure fluctuations during water evaporation in spouted bed

et al. 2009

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“…Bed temperature and residence time distributions (RTD) determine the thermal resistance of the materials in drying operations (22). However, in this study, RTDs seem to have had secondary importance only, as total IND recovery was obtained from microparticles which had adhered to the wall of the spouted bed chamber.…”

Section: Discussionmentioning

confidence: 92%

Impact of Cross-linking and Drying Method on Drug Delivery Performance of Casein–Pectin Microparticles

et al. 2013

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Abstract. Pectin is a heteropolysaccharide which has been investigated for the development of colonspecific drug delivery systems. Polymers have been associated with pectin to reduce its aqueous solubility and improve the performance of drug delivery systems. Pectin-casein interaction is widely known in food research, but it has not been fully considered by pharmaceutical scientists. Thus, this study investigated the potential of casein-pectin microparticles as a drug delivery system and clarified the impact of cross-linking and drying methods on the in vitro release of indomethacin (IND) or acetaminophen (PCT) from microparticles. Microparticles were prepared by coacervation and dried by spray or spouted bed methods. Drug recovery, in vitro drug release, size, morphology, and the thermal and diffractometric properties of dried microparticles were determined. Spray-dried non-cross-linked microparticles were able to prolong IND release, and pectin was still degraded by pectinolytic enzymes. On the other hand, glutaraldehyde cross-linking prevented the enzymatic breakdown of pectin without improving IND release. Spouted bed drying reduced IND recovery from all microparticles when compared with spray drying, thus the successful spouted bed drying of microparticles depends on the chemical characteristics of both the drug and the polymer. Release data from PCT microparticles suggested that the microparticle formulation should be improved to bring about a more efficient delivery of water-soluble drugs. In conclusion, casein-pectin microparticles show great potential as a drug delivery system because casein reduces the water solubility of pectin. The drying method and cross-linking process had significant effects on the in vitro performance of these microparticles.

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“…Because of that, this technique has been used to dry a variety of products ranging from chemical reagents to liquid foods and pharmaceuticals (Ochoa-Martínez et al, 1993;Szentmarjay et al, 1996;Reyes et al, 1998;Marreto et al, 2006;Pagliarussi et al, 2006), showing the feasibility of the process to dry heat sensitive products. In spite of this, very little information about the mean residence time and residence time distribution (RTD) of the product in the dryer has been reported (Fane et al, 1980;Berni and Freitas, 2007;Marreto et al, 2007;Tacon and Freitas, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Among the few works on this topic available in the literature, Marreto et al (2007); Berni and Freitas (2007); and Tacon and Freitas (2007) have recently published a series of three papers on the determination of RTD in a conventional spouted bed (CSB) with 2.6 mm glass beads or 3.4 mm polyethylene beads as inert particles, reporting on "the stimulus-response methodology," the "effect of spout operational conditions," and the "effect of paste properties and quality interactions," respectively. In these works, aqueous solutions of methylene blue were used as tracer, which was fed onto the bed of inert particles through an inlet pipe separately from the paste feed.…”

Section: Introductionmentioning

confidence: 99%

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. I: The Stimulus-Response Methodology

Cited by 5 publications

References 8 publications

Analysis of pressure fluctuations during water evaporation in spouted bed

Analysis of pressure fluctuations during water evaporation in spouted bed

Impact of Cross-linking and Drying Method on Drug Delivery Performance of Casein–Pectin Microparticles

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

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