Patent ID: 6221206
Filing Date: 2001-04-24
Classification: D21C

Abstract:
A method for oxygen delignification of a digested pulp comprising cellulosic material, said method comprising the steps of: initially delignifying said digested pulp at an initial delignification temperature of less than 90.degree. C. and an initial delignification pressure so as to produce a partially delignified pulp; adding oxygen to said digested pulp so that said oxygen is present during said initial delignification step; and subsequently delignifying said partially delignified pulp at a subsequent delignification temperature of greater than 90.degree. C., and a subsequent delignification pressure, without adding additional oxygen thereto, the difference between said initial delignification temperature and said subsequent delignification temperature being 0.degree. C. to 15.degree. C., said initial delignification pressure being greater than said subsequent delignification pressure, said method including adding alkali solely to said initial delignification step in order to obtain high alkalinity therein.