METHOD FOR PRODUCING ECF BLEACHED PULP

摘要

PROBLEM TO BE SOLVED: To provide a method for producing an ECF bleached pulp improving the whiteness of unbleached pulp without decreasing the unbleached pulp yield and effective for decreasing the total amount of bleaching chemicals in the ECF bleaching using chlorine dioxide as a main chemical. SOLUTION: The method for the production of an ECF bleached pulp comprises (A) a kraft digestion process using a lignocellulosic material of hardwood to carry out the kraft digestion at an available alkali concentration in black liquor of≥5 g/L and an H factor of≤700 at the end of digestion and giving a digested unbleached pulp having a kappa number of 15-18 and a whiteness of≥25%, (B) an oxygen bleaching process to carry out the bleaching treatment with oxygen and give a bleached kraft pulp having a kappa number of 9-11 and a whiteness of≥45% and (C) a multi-stage bleaching treatment in the ECF bleaching process using chlorine dioxide as a main chemical to set the addition amount of the total bleaching chemicals necessary for getting a whiteness of the ECF bleached pulp of 84-88% to 30-40 kg/pt in terms of the amount of available chlorine. COPYRIGHT: (C)2004,JPO