Improved elemental chlorine-free bleaching of hardwood kraft pulp

The investigation is aimed at elucidating the optimum technological scheme for bleaching as well as at the determination of the specific parameters of each stage, corresponding to the operation conditions applied in "Sviloza" Co., Bulgaria. The basic trends of the studies carried out are outlined by the requirements connected with the environmental aspects of the processes , and by the technical and economic characteristics of the pulp obtained. T he multistage process including two stage-bleaching with chlorine dioxide i s carried out along the following sequences: I:O-D-EO-D; II:O-EO-D-E-D. It is found that the first sequence provides greater effectiveness concerni ng the physico-mechanical indexes and brightness of the pulp obtained. The investigations carried out also include the application of a scheme with an enzyme stage of bleaching. The consumption of chlorine dioxide is reduced and more favourable technical and economical indexes of the bleached pulp a re reached.