Investigating the effect of using oxygen delignification process on kenaf bast kraft pulp properties

The first act to ameliorate bleaching process is the major elimination of lignin. Actually, the use of oxygen delignification stage before bleaching process is the essential stage in improving bleaching process and reducing process emission. In this study, the effect of conducting oxygen-delignifying process under different process condition, on chemical, physical, mechanical and optical properties of kenaf bast kraft pulp was investigated. The kenaf bast kraft pulp with the kappa number of 22, 1154 ml/g viscosity, and 38% ISO brightness was prepared. Oxygen-delignifying treatments were carried out with three different temperatures of 90, 100 and 110°C, and two oxygen pressures of 5 and 7 bars, with and without magnesium sulfate addition. Results indicated that oxygen delignification treatment led to intense decrease in pulp kappa number, while the pulp viscosity did not change significantly. Results of measuring delignified pulp viscosity showed that the magnesium sulfate addition caused to prevention of pulp viscosity downfall. The increase in reaction temperature had a significant effect on the process improvement, but raising the oxygen pressure did not have a meaningful effect on the process. Also, the pulp brightness was increased about 7%.