CONDEBELT BOARD AND PAPER DRYING

The history of development of the Condebelt process is outlined. The f unctioning principle of the various types of existing or proposed Cond ebelt dryers is clarified. Condebelt drying, being a type of press dry ing, imparts certain quality characteristics, due to the simultaneous high z-pressure and high temperature in the presence of moisture, to t he web. Some typical quality characteristics of Condebelt-dried sheets are presented for some usual paper and board grades. The web strength values of densified Condebelt-dried sheets are usually much higher th an those of conventionally dried sheets. This is mostly due to the muc h enlarged contact areas between flattened fibers, and to the flow of surface hemicellulose and lignin under the Condebelt drying conditions . In particular, wet strength values, as well as dimensional stability under changing environmental humidity conditions, are very much impro ved. Energy aspects of the process are also discussed, as well as proc ess runnability experiences.