Optimization of Drying of Coated Paper by Means of Automation, 1998 Coating Conference Proceedings

Please Note: This document will be available in PDF format in the "My Electronic Documents" link on the home page once your order has been completed. Please make sure you have the latest version of Acrobat Reader. Click on the Acrobat Reader icon to check for the latest version, it’s FREE. To print a hardcopy of a PDF file correctly you must have a postscript printer. If you are not sure if your printer is a postscript printer please refer to your owner’s manual.

The basic coating structure with its gloss and surface roughness variations is formed during coating consolidation. It has been known for a long time that incorrect drying power at the consolidation point lowers the end quality of coated paper an example is mottle. In order to improve the quality by use of automation, it is essential to know the location of the consolidation point and to determine the MD drying power across the drying section. Therefore, effective drying models are needed.

In the course of this study, a new drying optimization and regulation strategy was developed. The strategy is based on a simulation program which determines the development of moisture contents and evaporation rate of coated paper during the drying process. In the new control strategy, the controller optimizes the distribution of the required drying power to each drying unit in order to keep the consolidation point in the desired location and the drying power around the consolidation point at a moderate level. As a result, quality problems caused by the wrong drying are avoided. The end moisture is also kept at its setpoint by optimizing the drying power after the consolidation point.

Simulation and experimental results from a case study in a paper mill are discussed. It is shown that mottling is reduced significantly with the new control strategy,. The strategy can be used to resolve quality problems and to minimize energy usage encountered on a production machine. The on-line control system will maintain optimal drying conditions in a coater dryer section despite changing process conditions, and thus improve the quality of coated paper.