Methods of pulp fiber treatment

A method of treating pulp, comprising:

• feeding a source of a pulp in a forward-flow direction to a delignification process, and wherein the delignification process comprises:
• dewatering the pulp in a first wash stage, including separating first black liquor from the pulp;
• after the first wash stage, providing the pulp to a first fiber chest;
• after a residence time in the first fiber chest, subjecting the pulp to a second wash stage where the pulp is dewatered, and including separating second black liquor from the pulp;
• after the second wash stage providing the pulp to a second fiber chest;
• after a residence time in the second fiber chest, subjecting the pulp to a third wash stage where the pulp is washed with clean water and dewatered, and including separating third black liquor from the pulp;
• adding a parent oxidant solution to the pulp at a primary addition point and after the adding, mixing a mixture with the pulp with the added parent oxidant solution;
• and
• the parent oxidant solution being a peracetate oxidant solution to generate a reactive oxygen species in the resulting mixture, wherein the peracetate oxidant solution has properties as added to the pulp, wherein the properties comprise:
• a pH in a range of from pH 10 to pH 12;
• peracetate anions and a peracid with a molar ratio of peracetate anions to peracid of from 60:1 to 6000:1;
• and
• either no hydrogen peroxide or hydrogen peroxide wherein a peracetate anion to hydrogen peroxide molar ratio is greater than 16:1;
• and
• wherein after a period of time following the adding, separating from the pulp an oxidant liquor containing residual active oxidant and conveying the oxidant liquor to a secondary addition point, upstream of the primary addition point, where the pulp and the oxidant liquor are contacted and mixed;
• and wherein:
• the primary addition point is in the second washing stage;
• and
• the oxidant liquor comprises at least a portion of the third black liquor and the secondary addition point is in the first washing stage.

A method treating pulp, comprising:

• a delignification process, the delignification process comprising:
• adding a parent oxidant solution to a pulp at a primary addition point and after the adding, mixing a mixture with the pulp with the added parent oxidant solution;
• and
• the parent oxidant solution being a first peracetate oxidant solution to generate a reactive oxygen species in the resulting mixture, wherein the first peracetate oxidant solution has first properties as added to the pulp, wherein the first properties comprise:
• a pH in a range of from pH 10 to pH 12;
• peracetate anions and a peracid with a molar ratio of peracetate anions to peracid of from 60:1 to 6000:1;
• and
• either no hydrogen peroxide or hydrogen peroxide wherein a peracetate anion to hydrogen peroxide molar ratio is greater than 16:1;
• and
• wherein after a period of time following the adding, separating from the pulp an oxidant liquor containing residual active oxidant and conveying the oxidant liquor to a secondary addition point, upstream of the primary addition point, where the pulp and the oxidant liquor are contacted and mixed;
• bleaching the pulp with chlorine dioxide treatment after the delignification process, wherein the bleaching comprises a bleaching sequence of D0(PxO1)D1D2, except not including at least one of D1 and D2;
• and wherein the PxO1 is a bleaching stage comprising treatment of the pulp with a second peracetate oxidant solution having second properties when added to the pulp during the bleaching stage, wherein the second properties comprise:
• a pH in a range of from pH 10 to pH 12;
• peracetate anions and a peracid with a molar ratio of peracetate anions to peracid of from 60:1 to 6000:1;
• and
• either no hydrogen peroxide or hydrogen peroxide wherein a peracetate anion to hydrogen peroxide molar ratio is greater than 16:1;
• and
• wherein each said D is a treatment stage with chlorine dioxide and the PxO1 is a treatment stage of oxidative extraction with alkaline hydrogen peroxide.