Bleaching of kraft cellulosic pulp employing ozone and reduced consumption of chlorine containing bleaching agent

摘要

In a multi-stage bleaching sequence for kraft pulps employing a chlorine-containing bleaching agent in the first and final stages thereof and an intermediate alkaline extraction stage, the improvement for enhancing the brightness of the pulp and reducing the quantity of dioxin or chlorinated organics comprising contacting the pulp, in a mixer, at an acidic pH and a temperature of below about 60° C. with a mixture of ozone and oxygen at a pressure of between about 60 and 80 psig wherein the quantity of ozone introduced to the pulp is between about 0. 2% and about 0.4%, based on pulp.