It has been demonstrated in the laboratory that improved fibre-length control can be achieved by certain modifications of the LC-refining of ECF-bleached softwood kraft pulps. The rotational speed of the refiner affected immediately the fibre shortening tendencies. Increased speed resulted in extended fibre straightening as well as in a faster development of the drainage resistance. The effect of the rotational speed was consistent and present in all trials performed. The application of an inducer prior to the refiner may contribute to a reduced specific energy requirement by 10-15% for a certain drainage level. Fibre shortening may occur at a later stage with associated lower sheet strength. The inducer improved the fibre-length development, which consequently should provide positive effects on the sheet strength. Finally, increased bar-surface friction caused extensive fibre shortening. A normal friction straightens the fibres, whereas an increases friction may also cause excessive fibre tension, which reflects in a shorter fibre length.
展开▼
