CTMP Process Optimization Part III: On the Predicition of Scott-Bond, Z-strength and Tensile index

Artikel i vetenskaplig tidskrift, 2017

Here, the objective is to analyze estimates of the handsheet properties Scott-Bond, Z-strength and tensile index. It is shown that temperature profile measurements from the refining zones make it is possible to derive hidden physical phenomena that are impossible to measure inside the refining zones. Such measures are typical internal variables (consistency and fiber residence time) which can be used as predictors in multilinear models. The analysis is based on process data comprises three different chip mixtures. It is shown that the selected internal variables as predictors outperform the external variables (such as dilution water and plate clearance) in the polynomial fit. This is even more pronounced when validating the models using a holdout set. The methodology outlined in this paper makes it possible to model Scott-Bond, Z-strength and tensile index independently of the type of chip mixture when internal variables are used. It is also shown that the use of mean values of the handsheet properties can deteriorate the final model prediction considerably. Only about 60 % of all handsheet property samples were acceptable for modeling purposes. However, due to the extended laboratory test procedures a ranked and assured database as well as on-line models where possible to derive.