Modelling Relationships Between Wood and Fiber Properties and Thermo-Mechanical Pulp Properties Through a New TMP Pilot Unit Part 1: Description of the Method, 2001 Pulping Conference Proceedings

T. Fauchon, P. Mraz, G. Chantre, G. Dahlqvist, J. -C. Cleuet--The refining process has been characterized by Miles and May (1998), whose models show the influence of various process parameters and ways to increase its efficiency. The influence of the wood material on the process performance has, however, not been sufficiently understood. Some studies of the influence of Norway Spruce wood properties on TMP quality have, however, been performed. According to Tyrväinen (1995), the wood properties of Norway Spruce with the strongest impact in TMP manufacture are tracheid length, diameter and wall thickness, also reflected by the juvenile wood content. Uniform chip density and size distribution is of major importance for a well defined feeding of the refiner and uniform refining with constant energy consumption and conditions in the refining zone. The chip moisture content is also very important.

On the one hand, Wang and Braaten (1997) have underlined that rougher parameters, like log age, diameter or growth ring width, are not suitable for predicting TMP properties. They concluded that within each log class (top logs, butt/middle logs, thinnings) the relationship between growth ring width and pulp properties is rather weak. Logs age is useful to distinguish butt/middle logs from top logs and thinnings, but not good enough to distinguish thinnings from top logs.

On the other hand, Heikkurinen et al.(1999), have proved that diameter and height within the stem are good predictors for fiber length distribution, which is one of the most important factor of influence on the TMP quality. Nevertheless, the results don’t allow to establish strong cause and effect relationship between fiber length and TMP quality, other parameters varying in the same time.