Automatic Control of Additives with Modern Online Measurement Technology Raises Papermaker Productivity, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Information; Produ

Advanced on-line measuring technology enables automatic control of wet end additives in paper and paperboard machines. An important study from the Munich University of Applied Sciences was conducted on various paper machines to identify the benefits of controlling chemical dosages at different locations in the process.

In the framework of this study, fixatives (coagulant), retention aids and deaerator chemicals were put on automatic dosing control with on-line measuring devices on a high-speed newsprint machine in Sweden. Based on on-line cationic demand measurements, fixatives were controlled to a specific anionic trash set point. This control substantially increased chemical performance while simultaneously improving retention aid chemical performance and control.

On the paper machine, in-line consistency transmitters control retention aid chemical dosages resulting in more stable paper machine performance. Retention aid automatic control, based on white water consistency, is well known. It provides new opportunities for papermakers to enhance productivity via increased machine speeds, more stable retention and reduced wet end breaks.

On-line measurements of dissolved and entrained gases in the approach system enable controlling additions of deaerator chemicals into the white water. This study shows that stabilizing gas content provides significant cost savings.

When reviewing the overall results of the study, it was established that modern on-line measuring technology enables significant productivity increases for papermakers. On-line measurement allows adding chemicals strictly as required and avoiding over dosages. Controlling chemical additives enhances the stability of the machine and quality of the finished product.

This paper will show control strategies adopted in different areas of the paper mill and the benefits related to automatic closed loop control of wet end additives using the latest available measuring technologies.