Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Data and models for laboratory refining and pulp properties

Variations in paper properties may often originate from variations in wood properties. Better knowledge about the relationships between wood properties and properties of mechanical pulp is important for more efficient use of wood resources.

- AFOCEL has developed a TMP laboratory pilot refiner suitable for the refining of small wood samples. This two-stage laboratory procedure was used within the EU project EuroFiber which aims at the definition of wood assortments better adapted to the end-product qualities of different European paper mills with Thermo Mechanical Pulping plants.

- Norway spruce trees were sampled in four European countries (Estonia, France, Norway and Sweden). In each country many stands were selected and characterized in order to cover a maximum range of growth conditions, such as climate, site fertility and tree age. The stands were located in the wood supply areas of the participating mills to make industrial applications possible. Samples were taken at different heights of the trees and were split into juvenile, transition and mature wood, resulting in a total of 450 samples of Norway spruce with different properties.

- In a first step these wood samples were characterized with regard to the number of growth rings, mean ring width, latewood content, fiber morphology, density as well as chemical composition. In a second step the wood samples were processed with the two-stages refining procedure. Each pulp was characterized for physical and optical properties, fiber morphology and specific energy consumption. All these data on forest, wood and pulp properties were compiled and statistically analysed. Large variations in pulp properties within and between trees and between stands were observed in this study. Relationships between forest, wood and pulp properties were modelled.

- Models for pulp properties are issued from refining on the AFOCEL 12" laboratory refiner. Multiplicative model structure was found to be the best models type. As these models should be used to predict properties, process parameters, wood characteristics, assortment types, age and country were used as explanatory variables. These models could be used to increase pulp properties and evaluate how those properties will be affected by modifying wood and specific energy consumption, this one important factor showing the importance of controlling process conditions.

- AFOCEL could support EuroFiber partners on the application of these models to an industrial production, using these tools completed by others parameters available in the case of mill trials.

Benefiting from the large range of variations in the pulp properties, AFOCEL has also prospected the possibility to predict pulp quality directly from wood using NIR spectroscopy. This technology gives useable values for wood chemical composition prediction. Some limits exist for pulp properties based on wood NIRS spectra.

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