Maintaining Quality While Minimizing Costs in a DIP Mill, 2000 Pulping / Process & Product Quality Conference Proceedings

L. D. Ferguson, R. Shaw, R. DeBerry, C. Henriksson--For any mill, one of the keys to success is to minimize costs while maintaining product quality. This can be particularly challenging for a deinked pulp (DIP) mill due to the continuous variations in furnish quality and cost. Minimizing costs in a DIP mill starts with maximizing yield and optimizing unit operation performance. The unit operations are designed to separate the unwanted fraction (e.g. inks, fillers, stickies and debris) from the good fraction (e.g. fibre). Unfortunately, while removing the unwanted fraction, the unit operations also remove a portion of the good fibre fraction. A classification of each reject stream is required to determine where fibre can be recovered or retained without affecting product quality. In addition, continuous real-time yield information indicating losses from the system allows for quality and cost optimization.

Minimizing chemical costs is a second vital step in optimizing costs in a DIP mill. Similar to maximizing yield, the challenge is to minimize chemical costs without compromising quality. This can be achieved through strict control and the use of real-time chemical cost information. This information immediately allows the operations team to see the impact of chemical and production rate changes, and even downtime on pulp costs. It allows for a constant monitoring and immediate response to problem areas.

Over the past year, the use of reject stream classification and recovery, and utilization of continuos real-time yield monitoring has allowed the mill to improve yield by over 5% while maintaining production of premium quality DIP. Similarly, chemical optimization and continuous real-time cost monitoring have allowed chemical costs to be reduced by over 25% also while maintaining premium product quality. The paper looks at how the mill has achieved this.