Model Predictive Control of High Consistency Refiners, 2001 Process Control, Electrical & Info. Conference Proceedings

Greg Fralic, B.C. Strand, Said Mozaffari--At the Abitibi-Consolidated, Stephenville mill model predictive control (MPC) has been implemented on four lines of two stage high consistency chip refiners to control pulp quality. The controller is unique in that it coordinates the control moves on all four lines simultaneously. This allows the controller to use all available purchased power to achieve quality and production rate without exceeding power constraints.

The controller has proved the following benefits

* Decreased variability in pulp quality (freeness and fiber length)

* Decreased number of refiner trips due to power constraints

* Increased use of purchased power

* Increased production rate

Since start-up of the controller, the uptime has been approximately 97%. When combined with other MPC applications in the mill, the paper quality variability has decreased as much as 75%.

In this paper, the design and implementation of software sensors and MPC controllers will be described as well as the economic benefits that have been achieved for the mill.