Influence of Yield, Refining and Ingoing Solids on the Impulse Drying Performance of a Ceramic Coated Press Roll, 1992 Papermakers Conference Proceedings

Impulse drying is an innovative process for consolidation and drying of paper that holds great promise for reducing energy consumption and facilitating the use of higher percentages of recycled fiber. Early attempts to commercialize the process have demonstrated that sheet delamination is a major obstacle that must be overcome. Impulse drying research at the Institute of Paper Science and Technology (IPST) has focused on developing impulse drying process modifications that facilitate impulse drying of heavy weight grades while avoiding sheet delamination. Previously reported laboratory-scale experiments have shown that the thermal properties of the heated impulse drying roll have a significant effect on the maximum water removal that can be achieved without sheet delamination. In particular, it was found that by reducing the thermal conductivity and heat capacity of the press roll coating, impressive water removal could be achieved. The results of pilot impulse drying trials, conducted with a ceramic-coated press roll and a southern pine furnish, are presented. The experiments cover a range of Kappa number, refining levels and ingoing solids, yielding a range of ingoing sheet permeability. The experiments demonstrate that the roll temperature at which sheet delamination first occurs is a function of the specific surface of the ingoing web, which in turn is a function of; cooking, refining and pressing variables.