On the modeling of pulp properties in CTMP processes
Journal article, 2021

The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.


Pulp properties


Linear modelling

Fiber length


Fredrik Bengtsson

Chalmers, Electrical Engineering, Systems and control

Anders Karlström

Chalmers, Electrical Engineering

Torsten Wik

Chalmers, Electrical Engineering, Systems and control

Nordic Pulp and Paper Research Journal

0283-2631 (ISSN) 2000-0669 (eISSN)

Vol. 36 2 234-248

Subject Categories

Applied Mechanics

Probability Theory and Statistics

Control Engineering



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