Reducing Mill Energy Costs Using Pinch Analysis and apiMAX(TM) Process Simulator, 2003 Fall Technical Conference

Mill energy costs are still a major concern for many pulp and paper mills. Sophisticated software tools and techniques can be used to identify and evaluate potential operating and process changes, which will lead to reduced energy costs. Identifying operating and process changes are done using pinch analysis. A pinch analysis requires a mill-wide material and energy balance. A set of inconsistent data is usually available from a mill’s process information system. A mill-wide model is used to reconcile existing data and provide missing data. Pinch analysis uses this complete set of consistent data to determine the optimum (from an energy viewpoint) operating conditions for the mill. Comparing current mill operations with this optimum identifies energy savings options. Each of these options is evaluated, in detail using the mill-wide model, to determine the feasibility and the mill-wide impact of implementing the change. This methodology has been applied successfully to Weyerhaeuser Saskatchewan Ltd. Prince Albert mill.

The energy study carried out for this mill has shown that total steam savings of 97.6 t/h in the winter and 78.5 t/h in the summer can be achieved through process integration. The scope could be extended to a maximum total of 113 t/h in the winter, pending verification of some parameters. In addition to steam savings, modifications proposed after the operability review could result in increased black liquor recovery (fuel savings), bleach chemical savings and substantial water usage reduction.