ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Displacement washing of kraft pulp cooked from a blend of hardwoods

František Potůček and Jozef Miklík

Institute of Chemistry and Technology of Macromolecular Materials, Faculty of Chemical Technology, University of Pardubice, 532 10 Pardubice, Czech Republic

E-mail: frantisek.potucek@upce.cz

Received: 27 January 2009  Revised: 11 June 2009  Accepted: 27 June 2009

Abstract: The aim of this work was to investigate the displacement washing of kraft pulp manufactured from a blend of hardwoods. The experiments were carried out in a laboratory washing cell. In order to characterise the pulp fibres, the degree of freeness, kappa number, fibre length, as well as the specific volume and specific surface of swollen fibres were determined. The displacement washing process was described by displacement washing curves recorded for alkali lignin as a tracer. Mathematical treatment of the washing curves, obtained as a response to the step input signal, gave the Péclet number characterising the displacement of alkali lignin from the pulp pad. For detailed description of the displacement washing process, further parameters, such as the traditional wash yield, axial dispersion coefficient as well as the mean residence time and the space time were also evaluated. The results obtained for hardwood pulp were compared with those for softwood pulp published earlier. With respect to different chemical composition and morphological characteristics affecting both concentration of alkali lignin in mother liquor and physical properties of pulp pad, the displacement washing efficiency of hardwood pulp was found to be unambiguously greater in comparison with softwood pulp.

Keywords: displacement washing - hardwood pulp fibres - washing efficiency

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-009-0078-7

Chemical Papers 64 (2) 147–153 (2010)