Pulp Machine Control

Effective operation of the pulp machine can be extremely difficult. The basis weight and moisture content are very sensitive to small changes in the feed system and they are tightly coupled. Production rate changes must be based on very accurately timed changes in thick stock flow, speed, and dryer pressure to avoid upsets. And upset conditions can easily cause a sheet break resulting in lost production. 

Spartan Controls Advanced Solution’s Machine Control Strategy stabilizes the sheet machine direction (MD) basis weight and air dry (AD) content by employing a model-based multivariable control strategy. The model is based on machine speed, thick stock flow, headbox pressure or level, and dryer pressure and can easily be extended to include disturbances such as broke addition. Our control strategy stabilizes the sheet machine direction (MD) basis weight and air dry (AD) content by employing a model-based multivariable control strategy. 

Features:

  • Maximizing production is inherently included, so that system will automatically default to air dry control over basis weight control if the process is dryer limited
  • Fully automated production ramping is included.
  • Disturbance rejection is a key part of the system
  • Intelligent use of scanner data is built into the system
  • Flexible use of instrumentation is part of the design
  • Model deadtime varies based on the production rate, so that as the machine slows down, the feedback slows.
  • Model Predictive and Expert system logic for decision-making provides flexibility and the ability to respond effectively to the widest possible variety of real-time conditions.

Spartan implemented a process control optimization project on a pulp machine in northern BC. The Basis Weight and % Air Dry variability was reduced by over 60%, machine startups were 50% faster and overall production was optimized. This resulted in annual production benefit of over 3,000,000/year.

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