Enzyme Boosting and Peroxide Reinforcement in 100% Chlorine Dioxide Bleaching Sequences - A Low Capital Alternative to Oxygen Delignification, 1992 Pulping Conference Proceedings

Bleaching studies were made on softwood kraft pulp using a D100(EO)DED sequence - investigating the effect of decreasing kappa factor with the use of peroxide reinforcement, EOP- and E2P- stages, and enzyme bleach boosting, (X). The objective was to determine the impact on effluent quality and bleaching cost while maintaining market pulp brightness and viscosity. This could offer a low capital alternative to oxygen delignifi-cation. Results showed that low kappa factor bleaches with either D(EOP)D(EP)D or XD(EO)D(EP)D sequences could maintain both market pulp brightness and viscosity. Both effluent color and AOX decreased proportionally to the kappa factor. Compared to bleaching at 0.28 kappa factor, effluent colors were 30% lower, 70 kg/adt at 0.10 kappa factor. Similarly, AOX was 46% lower, 1.4 kg/adt.

Compared to oxygen delignification, the use of H202 and enzymes at 0.15 kappa factor produced equal brightness and equal AOX with slightly higher viscosity. Although bleach plant chemical costs are higher, including capital changes in bleach plant operating costs resulted in lower bleaching costs for the D (EO) D(EP)D or XD(EO)D(EP)D sequence compared to OD EO)DED.