Oxygen Delignification of Southern Softwood Kraft Pulps With High Lignin Content

摘要

The Kraft pulping process is more selective than the oxygen delignification process for removing lignin from the higher kappa number pulps (90 and 65). The lower selectivity of the oxygen delignification process was thought result from the presence of hydroxyl free radicals present in the oxygen delignification process that are not present in the Kraft pulping process. The alkali application rate was found to have a large effect on the rate of oxygen delignification. At a fixed temperature, the greatest reduction in kappa number was obtained by a high rate of application of alkali. This was true for both the high and low kappa number pulps. However, the alkali charge was found to have a high negative effect on pulp selectivity. Consequently, a balance must be achieved between lignin removal and pulp selectivity when selecting the alkali application rate.