Patent ID: 6221207
Filing Date: 2001-04-24
Classification: D21C

Abstract:
A method for the oxygen delignification of a chemical pulp which comprises contacting said chemical pulp with oxygen in an upstream reactor vessel having a top and a bottom by supplying said chemical pulp to said bottom of said upstream reactor vessel and withdrawing a partially oxygen delignified chemical pulp from said top of said upstream reactor vessel, maintaining a pressure of greater than about 3 bar in said upstream reactor vessel, contacting said partially oxygen delignified chemical pulp with oxygen in a downstream reactor vessel having a top and a bottom by supplying said partially oxygen delignified chemical pulp to said top of said downstream reactor vessel and withdrawing oxygen delignified chemical pulp from said bottom of said downstream reactor vessel, maintaining said downstream reactor vessel at a temperature of between about 90.degree. C. and 120.degree. C. and a corresponding predetermined pressure, and heating said partially delignified chemical pulp between said upstream and downstream reactor vessels by contacting said partially delignified chemical pulp with low pressure steam having a pressure of 2 bar or less.