Location study of cold caustic extraction (CCE) stage in a bleaching sequence of eucalyptus dissolving pulp

Abstract

The conversion of conventional kraft pulp to the dissolving pulp requires the hemicelluloses removal and activation of remaining cellulose. The extraction of the hemicelluloses was performed by alkali treatment using cold caustic extraction (CCE) and the activation of cellulose by peracetic acid (Paa) oxidation. The economic viability of the CCE process requires the recovery of alkali used and hemicellulose extracted in the process. The objective of this study was to evaluate the better position of the CCE stage in the pulp bleaching process, so as to facilitate recovery of the CCE filtrate. The raw material used was an industrial eucalyptus kraft pulp previously delignified with oxygen. The location of the CCE stage as the first stage of the bleaching sequence shown to be the most suitable for the production of viscose-grade pulp with the lower consumption of the bleaching chemicals and the best removal of the hemicelluloses from the pulp. The location of the CCE stage as the last stage of bleaching stage contributed to preserve the pulp viscosity, which would be interesting for acetate-grade pulp, which was less effective to remove the hemicelluloses.