Automatic Control of Additives with Modern Online Measurement Technology Raises Papermaker Productivity

摘要

Advanced on-line measuring technology enables automatic control of wet end additives in paper and paperboardrnmachines. An important study from the Munich University of Applied Sciences was conducted on various paperrnmachines to identify the benefits of controlling chemical dosages at different locations in the process.rnIn the framework of this study, fixatives (coagulant), retention aids and deaerator chemicals were put onrnautomatic dosing control with on-line measuring devices on a high-speed newsprint machine in Sweden. Basedrnon on-line cationic demand measurements, fixatives were controlled to a specific anionic trash set point. Thisrncontrol substantially increased chemical performance while simultaneously improving retention aid chemicalrnperformance and control.rnOn the paper machine, in-line consistency transmitters control retention aid chemical dosages resulting in morernstable paper machine performance. Retention aid automatic control, based on white water consistency, is wellrnknown. It provides new opportunities for papermakers to enhance productivity via increased machine speeds,rnmore stable retention and reduced wet end breaks.rnOn-line measurements of dissolved and entrained gases in the approach system enable controlling additions ofrndeaerator chemicals into the white water. This study shows that stabilizing gas content provides significant costrnsavings.rnWhen reviewing the overall results of the study, it was established that modern on-line measuring technologyrnenables significant productivity increases for papermakers. On-line measurement allows adding chemicalsrnstrictly as required and avoiding over dosages. Controlling chemical additives enhances the stability of thernmachine and quality of the finished product.rnThis paper will show control strategies adopted in different areas of the paper mill and the benefits related tornautomatic closed loop control of wet end additives using the latest available measuring technologies.