Method for bleaching paper pulp

A process for bleaching unbleached or pre-bleached paper pulp consisting of the following successive steps:

• a) preparing an unbleached or pre-bleached paper pulp with a pH greater than or equal to 8,
• b) placing the paper pulp obtained at the end of step a) in contact with chlorine dioxide,
• c) when the pH of the paper pulp at the end of step b) is less than 10, add at least one Brønsted base to the paper pulp,
• d) adding hydrogen peroxide to the paper pulp,
• e) keeping the paper pulp obtained at the end of step d) in a first bleaching tower,
• f) at the end of step e), acidifying the paper pulp and keeping it in a second bleaching tower,
• where the process has no step of washing the paper pulp before the end of step e).

A process for bleaching unbleached or pre-bleached paper pulp consisting of the following successive steps:

• a) preparing an unbleached or pre-bleached paper pulp with a pH greater than or equal to 8, wherein at least one cellulose protective agent and a chelating and/or sequestering agent are added during step a);
• b) placing the paper pulp obtained at the end of step a) in contact with chlorine dioxide;
• c) when the pH of the paper pulp at the end of step b) is less than 10, add at least one Brønsted base to the paper pulp;
• d) adding hydrogen peroxide to the paper pulp;
• e) keeping the paper pulp obtained at the end of step d) in a first bleaching tower, wherein the process has no step of washing the paper pulp before the end of step e).

A process for bleaching unbleached or pre-bleached paper pulp consisting of the following successive steps:

• a) preparing an unbleached or pre-bleached paper pulp with a pH greater than 8, wherein at least one cellulose protective agent and a chelating and/or sequestering agent are added during step a;
• b) placing the paper pulp obtained at the end of step a) in contact with chlorine dioxide;
• c) when the pH of the paper pulp at the end of step b) is less than 10, add at least one Brønsted base to the paper pulp;
• d) adding hydrogen peroxide to the paper pulp;
• e) keeping the paper pulp obtained at the end of step d) in a first bleaching tower;
• f) at the end of step e), acidifying the paper pulp and keeping it in a second bleaching tower, wherein the process has no step of washing the paper pulp before the end of step e).