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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Influence of the operating conditions on the heat transfer coefficient during agitated sludge drying

Get access (open in a dialog) DOI: 10.1615/IHTC12.690
6 pages

Abstract

In regard to the environmental legislation and regulation issues, partial or exhaustive drying offers significant reduction in the volume of the sludge output, and turns it into a valuable product. But the mechanical and thermal design of the dryers is still more a question of know-how than scientific knowledge. A batch laboratory scale dryer was developed to investigate the contact drying of sewage sludge. Drying kinetics, local and mean heat transfer coefficients at the dryer wall as well as the torque needed to keep a constant stirring speed can be determined. To validate this set up, the drying kinetics obtained in this batch dryer have been compared with kinetics determined in an industrial paddle dryer. The results are in good agreement. Then, this experimental tool was used to investigate the influence of the sludge origin, the wall temperature and the stirring speed on the mean heat transfer coefficient at the dryer wall. This gives some important information for the thermal design of the industrial process and for optimization.