Low consistency oxygen delignification process

摘要

A method for delignifying softwood or hardwood pulp taken from a fiber line of a pulp and papermaking system comprises adding oxygen to the pulp slurry and mixing the slurry under conditions of temperature and pressure whereby the oxygen reacts with lignin present in the pulp. The delignification is performed on pulp having a low consistency, i.e. containing less than 8% by weight of cellulosic material. The pulp for delignification is preferably taken from a point upstream of knotters in the papermaking system but downstream of brown stock washers so as to make effective use the residual alkali and heat content in the incoming black liquor.