Improved color and pH control using adaptive deadtime compensation

Using an advanced control method that reduces the effects of changes in process inputs and system response characteristics improved product uniformity and paper machine stability on two paper machines. The new adaptive method controls color on two paper machines and has reduced color variability more than 30%. The same method for improving control of wet-end pH on both machines has reduced variability more than 60%. Improved wet-end pH control has given 10% reduction in sizing chemicals and a significant improvement in sizing uniformity. The new adaptive strategy also reduced color and sizing rejects. Transport and measurement deloys or deadtime exist in many control loops in a pulp and paper mill and often result in less than optimal control. This paper presents an easy-to-use method to adapt the model to changing process conditions. Application : use of adaptive deadtime compensation provides color control, decreased wet-end pH variability, reduction in sizing chemicals, and improvement in sizing uniformity.