Chlorine Dioxide Reduction in ECF Bleaching of Kraft Pulp to High Brightness Through a Low Capital Enhancement of EOP Extraction, 1996 Pulping Conference Proceedings
Jeff A Stevens
Dr. Jeffery S. Hsieh
Georgia Institute of Technology
100% chlorine dioxide substitution followed by oxidative alkaline extraction is rapidly becoming the chief method of kraft pulp delignification for ECF bleaching. This D&op process can be improved so that less ClO2 is required in the initial Do stage to achieve full brightness after ECF bleaching, thus reducing formation of chlorinated organic compounds while reducing the C1O2 generator capacity required to reach full brightness. This work describes a process where sodium nitrite under acidic conditions is added just after the Do stage, without interstage washing, to “activate” the pulp for subsequent Eop extraction and DI D2 bleaching to full brightness. Using this technique, the kappa factor can be reduced from .18 to .15, while using only 1.3% CIO2 in the two downstream brightening stages to achieve 90 brightness.
Chlorine Dioxide Reduction in ECF Bleaching of Kraft Pulp to High Brightness Through a Low Capital E