Patent ID: 6174409
Filing Date: 2001-01-16
Classification: D21C

Abstract:
A method of bleaching a cellulose pulp using chlorine dioxide and ozone in one and the same single stage of a bleaching sequence having a plurality of stages, the method comprisinga. first establishing strength characteristics for said pulp when bleached in a control bleaching sequence by bleaching the cellulose pulp using chlorine dioxide and no ozone to a target brightness,b. establishing a set of curves using chlorine dioxide and ozone at different ratios in a single stage to bleach the cellulose pulp to determine a ratio of chlorine dioxide to ozone in a range effective to achieve strength characteristics at least as great as the strength characteristics of the control bleaching sequence, with the bleaching sequence used to establish said set of curves being the same in all respect with the control bleaching sequence of step a, except in that the control bleaching sequence of step a does not employ ozone in the single stage, andc. controlling the ratio of chlorine dioxide to ozone in a single stage of a first bleaching sequence in the determined range of step b which is effective to achieve strength characteristics of a final paper elaborated from the first bleaching sequence at least as great as the strength characteristics of the control bleaching sequence, where essentially the same final brightness of pulp is elaborated from the first bleaching sequence as in the control bleaching sequence.