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

AN EXPERIMENTAL EVALUATION OF THE LIQUID MOVEMENT IN THE PAPER COATING PROCESS Berg CG1, Rajala P.2 and Solin R.2 1. Process Design Laboratory, Department of Chemical Engineering, bo Akademi University, Biskopsgatan 8, FIN-20500 bo, FINLAND, cberg@abo.fi 2. Metso Paper OY, Air systems, Pansio, FIN-20240 Turku, FINLAND Key Words and Phrases: paper, coating, evaporation, hygroscopic, drying, porous media, sorption ABSTRACT This work will present the results of a study done on liquid movement, primarily during the coating and drying process, using either the bar or the blade coating method. The application of coating is discussed in order to elucidate how the water movement can be influenced after the coating station. In this study, it was found that the gross liquid transport into the paper during the coating process itself was influenced strongly by the state of the base paper and the coating, i.e. the sorption potential of the paper has a significant influence on the amount of water, which is transferred into it. It is also shown that a thin film in the coating develops already in the beginning of the coating process, and that this film may develop into a dominant restraint for vapor flow out of the coating. In addition to the state of the base paper, the pressure pulses and shear forces at the coating station may also affect the area of wetting (bonding area) between paper and coating layer, thereby influencing the film liquid movement.

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