D TEXTILES; PAPER
D21 PAPER-MAKING; PRODUCTION OF CELLULOSE
D21C PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
9/00 After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters; ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
D21C9/10 Bleaching; ; Apparatus therefor
D21C9/12 with halogens or halogen-containing compounds
D21C9/14 with ClO2 or chlorites
D21C9/144 with ClO2/Cl2 and other bleaching agents in a multistage process