Peroxygen Prebleaching and Bleaching Technologies for Step-Wise Conversion from Conventional Chlorine Bleaching Via ECF to TCF, 1993 Pulping Conference Proceedings

Environmental legislation and, even more, market pressure have forced the pulp and paper industry to explore alternatives to conventional chlorine based bleaching practices in the production of bleached kraft pulp. However, changing forces and goals can quickly render newly installed technologies either obsolete or unnecessary. In recent research work, prebleaching with hydrogen peroxide, mid-sequence Kappa-bridging with peracids, and final full brightening with P* hydrogen peroxide have been developed as three classes of peroxygen based bleaching technologies with excellent performance. Combinations of these technologies with oxygen in sequences of the type 0 Q P A P* (A = Paa, Ca) can bleach softwood kraft pulps to full brightness while maintaining adequate papermaking properties. They thus constitute a complete solution to the chlorine problem.

Peroxygen technologies provide technically feasible opportunities for a coherent, low risk, step-wise progress program towards environmentally acceptable bleaching, in three principal moves. Such strategies minimize initial capital spending to retrofit as much as possible existing mill configurations, delay major investment, and choose for investment which can satisfy evolving environmental constraints.