Retention of Fibers, Fillers and Fiber Fines at Individual Dewatering Elements of the Gap Former, 2002 Technology Summit Proceedings

M. Kosonen, J. Muhonen & J. S. Kinnunen

This paper presents a novel method of calculating the element retention of individual dewatering elements. It is based on a mass balance model of the forming and press sections which can be constructed when significant flows and consistencies are measured. If dry content of the paper after press is also known, the same model can be used to calculate precise dryness development along the wet end.

The proposed method was experimentally verified in a pilot machine producing 52g/m2 fine paper at a speed of 1200m/min. Total retention was varied between 50-75% by adjusting retention aid dosage. Simultaneously, all the major white water flows and total, ash, and fines consistencies were measured and element retentions of different stock components were determined. It was found that retention variation caused drastic changes in both element retentions and dryness development, which can also be seen in paper properties such as formation.