Zellstoff Pöls AG produces elemental chlorine-free (ECF) bleached softwood sulphate pulp as sheets which is sold under the brand name ORION sheet. The convective drying of the pulp web takes place in an airborne sheet dryer. During the last years the production volume has been increased continuously, which requires higher air temperatur within the dryer. This rise in temperature leads to increased occurance of heat-induced longterm yellowing of the pulp and whiteness losses. The purpose of this thesis was to examine pulp drying properties, causes of yellowing and operation conditions of the Zellstoff Pöls AG to gain control of the yellowing issue with laboratory and operating tests. The aim of these tests was to indentify opportunities to counter whiteness losses and to maintain quality standards despite increasing production volumes. Finally, based on the knowledge gained through the tests specific solution concepts have been developed in the form of operation recommendations and retrofitting measures for the web dryer. Nevertheless, for a precise cost-benefit assessment of the possible dryer modifications further investigations and tests are required.