The Effect of Chlorine Dioxide Charges in Chlorine Dioxide-Alkaline Extraction-Chlorine Dioxide (DED) Sequence on Optical Properties of Kraft Pulp ofEucalyptus Camaldulensis

Hardwoods are important raw material for making pulp and paper products. Eucalyptus camaldulensis is a fast-growing hardwood species with a wide distribution in Iran and can be introduced as appropriate material to compensate the wood shortages of the natural forest. Kraft pulping was performed under different cooking conditions and, based on the relations of pulp yield and kappa number, bleachable craft pulp at screened yield of 43.3% and kappa number of 31.3 was selected for DED (Chlorine Dioxide-Alkaline Extraction-Chlorine Dioxide) bleaching and its bleachability was studied at different kappa factor in D1 stage. The results indicated that the bleachable craft pulp from this species has high kappa number at acceptable screened yield and to complete the delignification in the bleaching process, higher kappa factor may be needed in DED bleaching sequence. The main reduction in final kappa number and yield loss were observed at kappa factor level of 0.2 but by further increase in kappa factor up to 0.4, more development were observed in optical properties but at lower opacity.