Oxygen Delignification of Bamboo Kraft Pulp with High Kappa Number

Bamboo kraft pulp with Kappa number of 25.6 was sampled, and oxygen delignification was applied to bleach these bamboo pulp samples. By investigating yield, Kappa number, viscosity, brightness of pulp, and delignification selectivity, it has been proven that caustic soda dosage and reaction temperature were major factors for oxygen delignification. The optimal conditions for oxygen delignification were proposed as follows: alkali dosage of 3.5% on o.d. pulp-mass, reaction temperature of 85°C, oxygen pressure of 0.6 MPa, and temperature retention time of 80 min. Two stages of oxygen delignification were used and no washing between the two was required. It was found that delignification efficiency and selectivity to lignin-removal were improved significantly. In addition, adding hydroquinone compounds during oxygen delignification can improve the qualities greatly such as higher viscosity and better selectivity of delignification.