The Dryer Section heats the paper to remove water by evaporation. The paper sheet winds its way over and under the cylinders while being pressed against them by felts. While in contact with each dryer cylinder, the paper absorbs heat. As the paper travels across the open pocket between cylinders, the heat is dissipated through the evaporation of water. The dryer section of the Fourdrinier machine dries the pulp by way of a series of steam-heated rollers that stretch the web somewhat, removing the moisture.
The dryer section plays an important role in paper machine operating efficiency, energy consumption and product quality. Accordingly, dryer section optimization is a high priority. In the area of dryer section control there is much room for improvement. Valve flaws, lack of instrumentation for diagnostics, and poor tuning all degrade regulatory loop performance. There are often no supervisory strategies in place to manage the drying load, respond to sheet breaks, optimize energy efficiency and deal with the fundamental non-linearities in the dryer loops. These supervisory strategies can be easily implemented in modern distributed control systems.