Effects of Cooking Conditions on the Bleachability of Bamboo Kraft Pulp

摘要

The bleachability of kraft pulp from wood has been the subject of several reports, but little effort has been made to assess the bleachability of nonwood pulp. This study evaluated the cooking conditions, such as active alkali charge, cooking time and sulphidity on the bleachability of bamboo kraft pulp. We cooked bamboo chips to kappa number around 20 by alternating cooking variables. We then quantified pulp yield, and evaluated pulp quality through measuring unbleached brightness, viscosity, pentosan, α-cellulose and phenolic hydroxyl group (PhOH) content in the residual lignin of pulp. Pulp produced at higher active alkali charge and sulphidity had higher pulp yield, higher α-cellulose, viscosity and lower pentosan in pulp and higher PhOH content in the residual lignin. After oxygen delignifying the pulp, bleaching was done by DED or QPP sequence. Degree of oxygen delignification had no relationship with the cooking conditions. The bleachability of pulps was determined by measuring consumption of chlorine dioxide to attain 80% brightness level. The bleachability of pulp was improved when pulping was done in higher active alkali charge and sulphidity. The bleachability of bamboo kraft pulp showed a direct relationship with PhOH content in the residual lignin.