Online Charge Measurements Enable Process Optimization and Automatic Control of Fixative Dosages, 2003 Spring Technical Conference Proceedings

For two decades, electric charges have been a vital parameter for quality monitoring of pulp suspensions. Most mill laboratories conduct charge measurements as a daily routine that is considered basic to quality assurance.

Although online charge measuring systems have been commercially available for some 15 years now, just a few hundred systems are currently installed in paper mills worldwide. Out of these, no more than 10 % are applied for automatic control of additive dosages. The reasons are many – they range from the functionality of available measuring systems up to the cost/benefit analyses and the selection of optimally suited fixative dosage points, where online charge analysis performs best.

Using the example of the Palm GmbH & Co. Eltmann mill, the authors demonstrate how modern papermakers can apply online charge measuring for automatic control of the charge character of their papermaking processes.

The Eltmann mill produces 430,000 t/a newsprint from 100 % recycled fiber on two paper machines. The first online system for charge analysis was installed on PM 3 in September 2001. Rated for a speed of up to 1700 m/min and commissioned in 1999, this paper machine accounts for an annual newsprint production of 245,000 t. Charge measurement was introduced with a view to gaining deeper insight into the process chemistry and to enhancing the performance of the strategic additives applied. Since November 2001, the fixative dosages into the approach flow have been under automatic control. In June 2002, a second charge analyzer was installed on PM 1. In this case, the objective is to avoid deposits and to reduce the charge level; thus, increase the machine runnability.