[en] Drying of two kinds of wastewater sludge was studied. The first part was an experimental work done in a discontinuous cross-flow convective dryer using 1 kg of wet material extruded in 12-mm-diameter cylinders. The results show the influence of drying air temperature for both sludges. The second part consisted of developing a drying model in order to identify the internal diffusion coefficient and the convective mass transfer coefficient from the experimental data. A comparison between fitted drying curves, well represented by Newton's model, and the analytical solutions of the equation of diffusion, applied to a finite cylinder, was made. Variations in the physical parameters, such as the mass, density, and volume of the dried product, were calculated. This allowed us to confirm that shrinkage, which is an important parameter during wastewater sludge drying, must be taken into account. The results showed that both the internal diffusion coefficient and convective mass transfer coefficient were affected by the air temperature and the origin of the sludge. The values of the diffusion coefficient changed from 42.35 × 10−9 m2 · s−1 at 160°C to 32.49 × 10−9 m2 · s−1 at 122°C for sludge A and from 33.40 × 10−9 m2 · s−1 at 140°C to 28.45 × 10−9 m2 · s−1 at 120°C for sludge B. The convective mass transfer coefficient changed from 4.52 × 10−7 m · s−1 at 158°C to 3.33 × 10−7 m · s−1 at 122°C for sludge A and from 3.44 × 10−7 m · s−1 at 140°C to 2.84 × 10−7 m2 · s−1 at 120°C for sludge B. The temperature dependency of the two coefficients was expressed using an Arrhenius-type equation and related parameters were deduced. Finally, the study showed that neglecting shrinkage phenomena resulted in an overestimation that can attain and exceed 30% for the two coefficients.
Disciplines :
Environmental sciences & ecology Chemical engineering
Author, co-author :
Bennamoun, Lyes ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Procédés et développement durable
Crine, Michel ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Opérations physiques unitaires
Léonard, Angélique ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Procédés et développement durable
Language :
English
Title :
Convective drying of wastewater sludge: Introduction of shrinkage effect in mathematical modeling
Publication date :
28 April 2013
Journal title :
Drying Technology
ISSN :
0737-3937
eISSN :
1532-2300
Publisher :
Taylor & Francis Ltd, New York, United States - New York
scite shows how a scientific paper has been cited by providing the context of the citation, a classification describing whether it supports, mentions, or contrasts the cited claim, and a label indicating in which section the citation was made.
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