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

FUTURE CHALLENGES IN DRYING OF PAPER Stig Stenström Lund Institute of Technology, Department of Chemical Engineering I P.O. Box 124, S-221 00 Lund, Sweden, E-mail: stig.stenstrom@kat.lth.se Keywords: paper, productivity, dynamics, diffusion, moisture gradients, quality ABSTRACT Productivity and paper quality are two of the most important parameters for the design and operation of the multi-cylinder paper dryer. Two important aspects for the productivity are a high drying rate and minimising production stops during capacity changes. Three levels of calculation methods for the drying rate, from simple graphical diagrams to computer based simulation tools, are presented and compared. Dynamical simulation models are important tools for the control of the paper dryer to reduce the time needed for quality changes and the development of such models is discussed. Drying rate as well as paper quality parameters are dependant on the internal moisture, temperature and pressure gradients and in order to enhance the paper quality, we need to better understand a number of the elementary physical mechanisms in the paper dryer. In this work vapour and liquid transport of water will be discussed as well as methods to measure moisture gradients.

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