Internal and External Factors Affecting the Paper Drying Process.

摘要

This study concentrated on factors affecting water removal in paper drying process, viewed from inside the paper structure and also from outside it. The aim of the thesis was to collect the essential factor affecting paper drying into a joint analysis. This main goal was divided into more detailed objectives. The effects of the factors on drying were studied based on the findings of earlier studies and the experiments carried out in this thesis. Sorption isotherm expressions were correlated with the measurement data. Thermodynamic factors, such as the sorption heat and the specific heat of sorbed water were derived from the sorption isotherm expressions. The specific heat of dry fiber material and its dependence on temperature and furnish was studied by means of sorption isotherms and specific heat values of moist fibers. Based on the results obtained, specific heat values dependent on the type of pulp and temperature should be used for the dry fiber material. The critical moisture content (CMC) was characterized from the air drying (desorption) curves. The CMC was not constant when the external drying parameters (air relative humidity, air temperature) were changed.