MORPHOLOGICAL CHARACTERIZATION OF PULPS TO CONTROL PAPER PROPERTIES

Recovered paper quality is a key issue for papermakers that intend to maintain the quality of their final products at a high and constant level, for meeting the consumer demands. However, since paper recovery is increasing, the quality of recovered paper is decreasing and, what is even worse, it varies along the time. The physical properties of recycled pulp fibres have a strong influence on most of the paper properties and, therefore, they play an important role in the establishment of the optimal papermaking conditions. These properties are directly related to the morphology of fibres and to pulp composition. In recent years, several new fibre and pulp morphological analyzers have been developed and released on the market. The use of online optical fibre analyzers allows papermakers to know the variations in pulp quality, enabling them to adjust the process and to maintain constant the quality of the paper produced. However, most of these devices are optimized for virgin fibres, their application for recovered paper being still limited. The present paper describes the modifications carried out in the programs of a fibre and pulp morphological analyzer (Morfi V7.9.13.E) to optimize its performance for the characterization of recycled pulps. The three programs (VESSELS, FIBRES and SHIVES) that the device includes by default have been considered and validated in a paper mill, producing different grades of newsprint and light-weight coated papers. The results show that, with the modified program, the device appears as a very promising tool to control and improve the final quality of recycled paper.