Improving the broke recirculation strategy in a newsprint mill

HEET BREAKS are a major disturbance in the newsprint process and cause costly paper machine downtime. Fluctuations in the pulp furnish can upset the stability of a paper machine and are one of the causes of breaks. These fluctuations can be the result of the broke recirculation strategy applied at the mill. Specifically, sudden changes to the broke ratio can induce considerable variations in the properties of the mixed pulp at the paper machine headbox [7]. Broke recirculation strategies can be quantified and explored by the application of simulation-based optimization. This technique is increasingly being used in other applications, and has been shown to yield significant economic benefits at low investment cost and little disturbance to the actual process [3,6]. This study focuses on developing a dynamic simulation of the papermaking section of an integrated newsprint mill, and using an objective function to quantify fluctuations at the headbox. Direct search optimization was then applied to identify opportunities for improving the broke recirculation strategy at the mill. The overall goal was to reduce headbox variability caused by adjustments in the broke ratio.