Predictive Adaptive Control Aids Pulp Digestion

igestion is a hot topic in pulp production at Skeena Cellulose in Prince Rupert, British Columbia, Canada. A new continuous digester control system uses a new predictive adaptive process controller to provide closed-loop control of Effective Alkali and reduced Kappa Number variability. The installation of this controller has resulted in production cost savings of $0.60 per ton of pulp and projected savings of more than $100,000 annually for each of two digesters. Production deviations have been reduced, yielding more uniform and salable pulp. To achieve these results, Skeena is using Brain Wave, a new predictive adaptive process controller capable of controlling processes with long dead time and automatically adapting to process changes. Previous predictive controller designs (such as Smith Predictor and other model-based controller designs) at the Skeena mill had been inadequate because of an inability to adapt to variations in process dead time as well as the setup and maintenance required.