Molded pulp products with structural capabilities have recently been demonstrated for packaging applications and sheathing panels (eg. FPL Spaceboard). A significant barrier to their full implementation in industrial products and shelter systems is the amount of time required to dry these water-formed products. A research study was initiated to utilize a new drying concept for paperboard (termed Condebelt) which greatly increased drying rates, decreased energy requirements and provided Z-direction restraint. The concept's application to the arena of thick molded pulp structures requires a fundamentally-based approach to improve drying technology.
In its basic configuration the Condebelt drying process can be summarized as follows. A molded structure comprised of a 3-dimensional wet fiber structure and a 3-dimensional silicone mold are placed in a sealed chamber having the top platen hot and the bottom platen cold. In the sealed chamber, the hot platen contacts the wet mass and through a variety of phenomena, moves the water to the cold platen surface, compacts the molded pulp, and dries the pulp-based product. Due to the wide array of hot/cold platen temperatures, the ability to evacuate the press chamber, and the dynamics of the mold/product hygro-thermal characteristics; the optimization of the drying process will be undertaken from the analytical perspective. For verification of the analysis, a series of drying trials were completed using a well instrumented laboratory device at Valmet Tampella's Inkeroinen, Finland facility.
In this presentation three aspects of the program will be highlighted: 1) The Analytical Approach. Simulation of the drying process will show how the time-based numerical integration/analysis will use implicitly determined coefficients to advance the understanding of heat and mass transfer in such complex drying systems. 2) Preliminary Results. The drying trials using the new drying concept will be shown and contrasted with traditional drying approaches. 3) Molded Pulp Products. Concepts for molded pulp use in structural applications will be used to demonstrate the potential of this class of materials and their compatibility with agricultural or unsorted waste paper fiber.
Key words: pulp, drying, molding, modeling.
Correspondence: Margit Tamasy-Bano, Univ. of Forestry and Wood Science, H-9400 Sopron, P.O.B. 132, Hungary
Telefax: +36-993-11103