High Temperature Chlorine Dioxide Delignification: A Breakthrough in ECF Bleaching of Hardwood Kraft Pulps, 1998 Pulping Conference Proceedings
High temperature (95°C) ClO2 delignification is shown to be more efficient than a conventional D stage performed at lower temperature (45°C). With hardwood kraft pulp, 20 to 30% ClO2 can be saved at the same DE kappa number, provided that the time in D is long enough (1.5-4 hrs). This would be due to the effect of the acid medium, which at 95°C degrades the hexenuronic acids and may also affect the lignin structure. This is confirmed by the fact that a AD sequential treatment where a hot acid stage precedes a conventional D stage gives a similar result.
Another way to achieve the same improvement is to raise the temperature to 90-100°C at the exit of the conventional D stage and to maintain it for several hours.
High Temperature Chlorine Dioxide Delignification: A Breakthrough in ECF Bleaching of Hardwood Kraf
