Abstract: A process for the bleaching of chemical pulp, wherein the initial bleaching of the pulp includes a first chlorine dioxide treatment (D0) and a following alkaline treatment with oxygen and hydrogen peroxide (EOP), which stages are separated from each other with a washing stage, and a treatment of the pulp to reduce the content of transition metals of the pulp prior to the peroxide treatment. The process is characterized in that alkali is added to the pulp after addition of chlorine dioxide in the D0 stage to adjust the pH of the pulp to neutral or basic (N stage) prior to the washing stage following the chlorine dioxide stage, whereby the initial bleaching includes the sequence D0N EOP.

Abstract: A process for the bleaching of chemical pulp, comprising a first chlorine dioxide treatment (D) of the initial bleaching and chelation (Q) to be carried out in connection therewith, forming together a DQ treatment. The process is characterized in that the chelation is carried out at the pH of from 2 to 7, and it is followed by an alkalizing stage (N) of the pulp, without intermediate washing for raising the pH of the pulp to above 7 and at most to 12 prior to a following stage which is a washing step.