Coating and Drying in Spouted Bed: Influence of the Liquid-Particle Work of Adhesion

Donida, Marta Wilk; Rocha, Sandra Cristina dos Santos; Castro, Beatriz; Marques, A. M. M.

doi:10.1080/07373930601119904

Cited by 18 publications

(13 citation statements)

References 8 publications

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“…Several problems might arise during the spouted bed drying of these products including bed instability, coating of inert bodies, particle growth and product agglomeration and bed collapse (Oliveira and Souza, 2008). These problems can be related to the physicochemical properties of the feed composition and inert bodies, as well as equipment configuration and operating conditions (Souza et al, 2006, 2009; Donida et al, 2007). The addition of drying carriers to the ESs before drying can improve the drying performance and the quality attributes of dried product.…”

Section: Introductionmentioning

confidence: 99%

Drying of herbal extract in a draft‐tube spouted bed

Souza

Oliveira

2009

Can J Chem Eng

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This work evaluates the feasibility of the draft-tube spouted bed for drying of herbal extract. Drying runs were carried out according to a central composite design in a conical-cylindrical draft-tube spouted bed. The variables studied were the percentage of the drying aid (ADJ), the drying gas flow rate relative to gas flow at minimum spouting (Q/Q ms ), and the flow rate of extract fed to the system relative to the spouting gas flow rate (W s /W g ). Colloidal silicon dioxide was the drying aid used in order to improve drying performance. Statistical analysis of the effects of processing parameters on product recovery, product accumulation in the bed, and product properties permitted the identification of parameters presenting significant effects on drying. Optimized drying conditions were related to experimental parameters as follow: high levels of the percentage of drying adjuvant (ADJ), high airflow rate relative to minimum spouting (Q/Q ms ), and low values of the feed flow rate of the extract relative to the gas flow rate (W s /W g ).

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Section: Introductionmentioning

confidence: 99%

Drying of herbal extract in a draft‐tube spouted bed

Souza

Oliveira

2009

Can J Chem Eng

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“…Due to the bad wettability and consequent weak adhesion, the film involving the particles takes off as coarse particles and even as small peaces of dry film and accumulates inside the bed. The solids retention in the bed causes fluid dynamic instability with decreasing particles circulation rate and bed pressure drop, as also verified by Donida et al (2007) and stated in the literature about drying of pastes in spouted beds (Schneider and Bridgwater, 1993;Spitzner Neto and Freire, 1997;Medeiros et al, 2002).…”

Section: Performance Of the Coating Processesmentioning

confidence: 56%

“…• (five formulations of aqueous polymeric suspensions and particles of polystyrene (PS), polypropylene (PP), and low density polyethylene (LDPE)), as the dry film-particle adhesion was not strong enough (Donida et al, 2004(Donida et al, , 2007. Coating of particles occurred for contact angles lower than 70…”

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confidence: 99%

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Liquid‐particle surface properties on spouted bed coating and drying performance

2009

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Polymeric coating has been applied to particles for several reasons, which goes from enhancing product esthetics to control the release of chemicals. Spouted beds are among the equipments widely used to coat particles. Its choice is justified by the cyclic movement of the particles in stable spouting resulting in product homogeneity and good solid-fluid contact with high heat and mass transfer rates. Also, the spouted bed with inert particles is an alternative to drying pastes due to its low cost and applicability to low scale production. This work presents results of coating and drying efficiencies for different systems that combine 04 different solids and 03 formulations of suspensions. Materials having different surface tension were chosen and suspensions with varying surface tensions were formulated, resulting in different wettabilities (quantified by contact angles measurements). The results show the direct influence of these properties on the coating and drying performances.On applique un revêtement polymérique aux particules pour plusieurs raisons, qui vont de l'amélioration de l'esthétique du produit jusqu'au contrôle du rejet de substances chimiques. Les lits en jaillissement sont parmi leséquipements les plus couramment utilisés pour revêtir les particules. Leur choix se justifie par le mouvement cyclique des particules dans des conditions de jaillissement stable, qui donne en bout de ligne une homogénéité du produit et un bon contact entre les solides et les fluides et des coefficientsélevés de transmission de chaleur et de transfert de masse. De plus, le lit de jaillissement alimenté de particules inertes est une solution de rechange au séchage des pâtes en raison de son faible coût et de ses possibilités d'applicationà la productionà petiteéchelle. Cet ouvrage présente les résultats relativement aux rendements du revêtement et du séchage de différents systèmes combinant quatre solides différents et trois formulations de suspensions. On a choisi des matériaux qui ont une tension superficielle différente et on a formulé des suspensions ayant diverses tensions superficielles, ce qui a donné lieuà des mouillabilités différentes (quantifiées par les mesures des angles de contact). Les résultats montrent l'influence directe de ces propriétés sur les rendements du revêtement et du séchage.

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“…Nestas duas operações a suspensão alimentada recobre as partículas, movimentadas por ar aquecido, formando uma película líquida delgada. Na secagem, o filme depositado sobre as partículas seca e o atrito entre estas provoca o rompimento do material aderido que é arrastado na forma de pó, enquanto no recobrimento, o sólido permanece unido à partícula após a evaporação do solvente (DONIDA et al, 2007).…”

Section: Revisão Bibliográficaunclassified