A complete automation solution for production management and quality control of the batch digester process. SmartProcess COOK has many successful installations for both the kraft pulping and sulfite pulping processes. The solution includes control of all digester sequences from liquor and chip filling to the final blow. Digester scheduling and model-based cooking control are at the core of the solution. Emerson provides a comprehensive operator interface and production and quality reports, all custom-developed for the mill in which it is installed.

Improvement Highlights • Variability Reduction: 20 - 40%. • Production Increase: 2- 10%. • Steam Reduction: 5 - 15%. Objectives/Benefits • Production Management Improvement:   optimize digester scheduling, increase yield . • Quality Improvement: lower kappa variability   from batch to batch, decrease rejects. • Reduce Energy and Chemical Usage:    optimize the usage of steam and cooking   liquor. • Improve Downstream Processes: improved   washer efficiencies, reduce bleaching   chemical costs, improve paper machine   efficiency. • Improve Safety: improve reliability of   interlocking, decrease operator work load,   enforce standard operating procedures   (SOPs).

SmartProcess® Cook primary control modules:

- Chip Filling Control - Blow Control
- Liquor Filling Control - Digester Scheduling
- Steaming Control - Steam Limiting and Smoothing Controls
- Cooking Control - Pulp Quality Control
- Relief Control - Grade Change Control

SmartProcess® Cook for Batch Digesters Background

At the head of the pulp and paper mill’s fiberline is the batch digester house. This process area greatly effects quality and efficiency in downstream operations. In a batch digester house, minimizing pulp quality variation while maintaining production goals is a very tough challenge. Variations in wood properties and cooking liquor strengths must be compensated for. Chip and liquor filling, temperature rise, and digester cooking must be carefully controlled to maintain consistent pulp quality. Sequencing of digesters must be managed to prevent process upsets and hazardous conditions. In order to meet production targets, digester blow schedules must be maintained and optimized. It is easy to see why controlling the operations in a batch digester house is so demanding.

SmartProcess COOK controls chip and liquor filling of the digesters to insure proper chip packing and alkali/wood and liquor/wood ratio. The digester temperature rise is carefully controlled to bring the digester to the cooking temperature target. An adaptive cooking model controls the cook. The digester pressure is controlled throughout the cook with the blowback valve.

The cooking model determines the completion of the cook. SmartProcess COOK controls the valves for the digester blow sequence while monitoring process levels to insure a smooth and safe sequence. The application can be setup for operators to confirm digester sequence steps such as blow, uncap, fill, and steam. Transitions to these steps can be completely automatic if desired.

The Digester Scheduling control manages digester schedule with respect to the limitations of the digester house equipment and available steam supply. The digesters are synchronized in order to preserve minimum intervals between cooking phases, prevent blow collisions, and meet production rate targets.

Pulp quality is controlled by a model-based cooking algorithm which determines the required alkali-to-wood ratio and the length of the cook. SmartProcess COOK can incorporate online analyzers, if available, for Kappa No. and liquor strength.