1st Nordic Drying Conference - NDC'01, Trondheim, Norway, June 27-29, 2001

FORMATION OF FOULING LAYERS AND EFFICIENT ENERGY RECOVERY FROM DRYER EXHAUST GASES Steffen Kaiser and Evangelos Tsotsas Otto-von-Guericke-University, Thermal Process Engineering, P.O. Box 4120, 39016 Magdeburg, Germany, E-mail: Evangelos.Tsotsas@vst.uni-magdeburg.de Keywords: drying, exhaust gas, fouling, energy recovery, heat transfer ABSTRACT The majority of industrial dryers are offered and operated without efficient energy recovery. This is astonishing and disadvantageous in consideration of the very high energy consumption of drying processes. A main reason for this is, that the warm dryer exhaust gases contain condensable vapors as well as fine solid particles. Therefore, they incline to condensation and the formation of fouling layers on cold heat transfer surfaces. The avoidance of fouling is the key issue concerning an efficient heat recovery from dryer exhaust gases. The objective of the present investigations is a phenomenological description and quantification of the dynamics of fouling layer formation. Selected results, gained with a specialized facility, are presented and discussed. The phenomenology of the experimental findings will be analyzed along with first attempts for theoretical interpretation and correlation.

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