Patent ID: 8568558

Claim:
A process for delignifying and bleaching chemical pulp, comprising a bleaching stage, wherein: a) in a first step, chemical pulp in a first aqueous mixture containing 3 to 30% by weight of said chemical pulp is reacted with chlorine dioxide in an amount corresponding to a Kappa factor in the range from 0.02 to 0.25, at a temperature of 50 to 150° C. and a pH in the range of from 2 to 7, until more than 90% of the chlorine dioxide has reacted, thereby forming a second aqueous mixture; and b) in a second step, the second aqueous mixture obtained in the first step is further reacted, without separating off constituents of the second aqueous mixture, with 0.1 to 5% by weight of hydrogen peroxide in the presence of a molybdate in an amount of 10 to 2,000 ppm of molybdenum or of a tungstate in an amount of 200 to 10,000 ppm of tungsten, at a temperature of 50 to 150° C. and a pH in the range of from 2 to 7, the amounts being based in each case on the mass of dry chemical pulp used, thereby forming a third aqueous mixture.