convective drying; sludge; transfer coefficients; kinetics; evaporation capacity
Abstract :
[en] The influence of air temperature, velocity, and humidity during convective drying of two different sludges (A and B) is investigated through a 3 3 factorial design. For sludge A, a constant drying flux period is observed, while sludge B is characterized by a long decreasing drying flux phase. A sensitivity analysis shows that temperature is the main operating parameter affecting the drying kinetics. Mass and heat transfer coefficients as well as water evaporation capacities are calculated from drying curves. Transfer coefficients are related to operating conditions through dimensionless relations. For both sludges, a linear relation is found between water evaporation capacity and the maximal measured drying flux.
Disciplines :
Chemical engineering Mechanical engineering
Author, co-author :
Léonard, Angélique ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Opérations physiques unitaires - Département de chimie appliquée
Blacher, Silvia ; Université de Liège - ULiège > Département de chimie appliquée > Labo de génie chimique
Marchot, Pierre ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Systèmes polyphasiques
Pirard, Jean-Paul ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Génie catalytique
Crine, Michel ; Université de Liège - ULiège > Département de chimie appliquée > Génie chimique - Opérations physiques unitaires
Language :
English
Title :
Convective drying of wastewater sludges: Influence of air temperature, superficial velocity, and humidity on the kinetics
Alternative titles :
[fr] Séchage convectif de boues d'épuration : influence de la température, de la vitesse superficielle et de l'humidité de l'air sur la cinétique
Publication date :
2005
Journal title :
Drying Technology
ISSN :
0737-3937
eISSN :
1532-2300
Publisher :
Taylor & Francis Inc, Philadelphia, United States - Pennsylvania
Conseil de l'Union Européene. 1999. Directive 1999/31/EC du 26 avail 1999 du Conseil relative à la mise en dècharge des déchets. OJ L 182 16.07.1999.
Conseil de l'Union Européene. 1991. Directive 1991/271/EC du 21 mai 1991 du Conseil relative au traitement des eaux urbaines résiduaires. OJ L 135 30.05.1991.
Hassebrauck, M.; Ermel, G. Two examples of thermal drying of sewage sludge. Water Science and Technology 1996, 33, 235-242.
Kazakura, T.; Hasatani, M. R&D needs - Drying of sludges. Drying Technology 1996, 14, 1389-1401.
Carrère-Gée, C.; Lecomte, D.; Fudym, O.; Ledevie, B.; Vasseur, J. Determination of heat flux in thin layer drying of sludges. In Drying '98 - Proceedings of the 11th International Drying Symposium (IDS'98); Akritidis, C.B.; Marinos-Kouris, D.; Saravacos, G.D. Eds.; Thessaloniki, Greece, 19-22 August 1998; 695-702.
Léonard, A.; Crine, M. Relation between convective drying kinetics and shrinkage of wastewater treatment sludges. In Proceedings of the 12th International Drying Symposium; Paper no. 131, Noordwijkerhout, The Netherlands; Kerkhof, P.J.A.M.; Coumans, W.J.; Mooiweer, G.D. Eds.; Amsterdam: Elsevier Science B.V., 28-31 August 2000.
Ferrasse, J.-H.; Arlabosse, P.; Lecomte, D. Heat, momentum, and mass transfer measurements in indirect agitated sludge dryer. Drying Technology 2002, 20, 749-769.
Vaxelaire, J.; Puiggali, J.R. Analysis of the drying of residual sludge: From the experiment to the simulation of a belt dryer. Drying Technology 2002, 20, 989-1008.
AFNOR. Tests on sludges - Determination of properties related to thickening capacity. AFNOR T 97-001, Paris, 1979.
Léonard, A.; Blacher, S.; Marchot, P.; Crine, M. Use of x-ray microtomography to follow the convective heat drying of wastewater sludges. Drying Technology 2002, 20, 1053-1069.
Moreira, R.; Figueiro, A.; Sereno, A.A. Shrinkage of apple disks during drying by warm air convection and freeze drying. Drying Technology 2002, 18, 279-294.
Lozano, J.E.; Rotstein, E.; Urbicain, M.J. Shrinkage, porosity and bulk density of foodstuffs at changing moisture contents. Journal of Food Science 1983, 48, 1497-1553.
Léonard, A.; Blacher, S.; Marchot, P.; Pirard, J.P.; Crine, M. Measurement of shrinkage and cracks associated to convective drying of soft materials by x-ray microtomography. Drying Technology 2004, 22, 1695-1708.
Serra, J. Image Analysis and Mathematical Morphology, Vol. 1; Academic Press: New York, 1982.
Coster, M.; Chermant, J.L. Précis d'analyse d'images; CNRS: Paris, 1985.
Léonard, A.; Blacher, S.; Marchot, P.; Pirard, J.P.; Crine, M. Image analysis of x-ray microtomograms of soft materials during convective drying. Journal of Microscopy 2003, 212, 197-204.
Coumans, W.J. Models for drying kinetics based on drying curves of slabs. Chemical Engineering and Processing 2000, 39, 53-68.
Welty, J.R.; Wicks, C.E.; Wilson, R.E.; Rorrer, G.L. Fundamentals of Momentum, Heat and Mass Transfer, 4th Ed; John Wiley & Sons: New York, 2001.
Simal, S.; Rossello, C.; Berna, A.; Mulet, A. Drying of shrinking cylinder-shaped bodies. Journal of Food Engineering 1998, 37, 423-435.
Perré, P. Macroscopic equations to simulate heat and mass transfer. In Mathematical Modeling and Numerical Techniques in Drying Technology; Turner, I., Mujumdar, A.S., Eds.; Marcel Dekker: New York, 1997; 83-156.
Geankoplis, C.J. Transport Processes and Unit Operations; Prentice-Hall: Englewood Cliffs, NY, 1993.
Whitaker, S. Forced convection heat transfer correlations for flow in pipes, past flat plates, single cylinders, single spheres, and for flow in packed beds and tube bundles. AIChE Journal 1972, 18, 361-371.
Ratti, C.; Mujumdar, A.S. Simulation of packed bed drying of foodstuffs with airflow reversal. Journal of Food Engineering 1995, 26, 259-271.
