Patent ID: 6841036

Claim:
A process for the oxygen delignification of a pulp consisting of a lignocellulose-containing material, comprising: conveying pulp from a first pump to a first mixer and adding oxygen to the first mixer; in a first stage extending from an outlet of the first mixer to an inlet of a second pump, performing oxygen delignification in which the pulp is being treated for a first time period of between 2-20 minutes at a first pressure and a first temperature of between about 75-95 C; conveying the pulp to the second pump; adding oxygen to a second mixer and conveying the pulp to the second mixer downstream of the second pump; in an oxygen reactor, performing oxygen delignification in which the pulp is treated for a second time period that is longer than the first time period at an over-pressure and a second temperature, the over-pressure being higher than the first pressure in the first stage.